RAD Studio - Recent changes [en]

Connecting to a Data Store Using TADOConnection

WikiSysop — Tue, 14 Jul 2026 18:12:06 GMT

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	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	ADODataSet1.Connection := ADOConnection1;		ADODataSet1.Connection := ADOConnection1;
	</~~source~~>		</syntaxhighlight>

	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	ADODataSet1->Connection = ADOConnection1;		ADODataSet1->Connection = ADOConnection1;
	</~~source~~>		</syntaxhighlight>

	The connection component represents an [[Accessing the Connection Object\|ADO connection object]]. Before you can use the connection object to establish a connection, you must identify the data store to which you want to connect. Typically, you provide information using the ADOdb.TADOConnection.ConnectionString property. ''ConnectionString'' is a semicolon delimited string that lists one or more named connection parameters. These parameters identify the data store by specifying either the name of a file that contains the connection information or the name of an ADO provider and a reference identifying the data store. Use the following, predefined parameter names to supply this information:		The connection component represents an [[Accessing the Connection Object\|ADO connection object]]. Before you can use the connection object to establish a connection, you must identify the data store to which you want to connect. Typically, you provide information using the ADOdb.TADOConnection.ConnectionString property. ''ConnectionString'' is a semicolon delimited string that lists one or more named connection parameters. These parameters identify the data store by specifying either the name of a file that contains the connection information or the name of an ADO provider and a reference identifying the data store. Use the following, predefined parameter names to supply this information:

Connecting the Client to DataSnap Server

WikiSysop — Tue, 14 Jul 2026 18:12:04 GMT

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	DataModule2.SQLConnection1.Close;		DataModule2.SQLConnection1.Close;
	DataModule2.ServerMethods1Client := nil;		DataModule2.ServerMethods1Client := nil;
	</~~source~~>		</syntaxhighlight>
	<l e="delphi" />		<l e="delphi" />

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	end;		end;
	end;		end;
	</~~source~~>		</syntaxhighlight>
	<l e="delphi" />		<l e="delphi" />
	}}		}}
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	http.Free;		http.Free;
	end;		end;
	</~~source~~>		</syntaxhighlight>
	<l e="delphi" />		<l e="delphi" />

Connect to Sybase SQL Anywhere (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:12:03 GMT

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	Setup=/Applications/SQLAnywhere12/System/lib32/libdbodbc16_r.dylib		Setup=/Applications/SQLAnywhere12/System/lib32/libdbodbc16_r.dylib
	UsageCount=1		UsageCount=1
	</~~source~~>		</syntaxhighlight>

	* remove '''libodbcinst.dylib''' and '''libodbcinst.dylib.1''' links from '''/Applications/SQLAnywhere12/System/lib32''' folder, as they conflict with UnixODBC '''libodbcinst.dylib'''. This action is recommended by the Sybase development team.		* remove '''libodbcinst.dylib''' and '''libodbcinst.dylib.1''' links from '''/Applications/SQLAnywhere12/System/lib32''' folder, as they conflict with UnixODBC '''libodbcinst.dylib'''. This action is recommended by the Sybase development team.
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	echo Setup=/opt/sqlanywhere16/lib64/libdbodbc16_r.so >> asa.driver.template		echo Setup=/opt/sqlanywhere16/lib64/libdbodbc16_r.so >> asa.driver.template
	sudo odbcinst -i -d -f asa.driver.template		sudo odbcinst -i -d -f asa.driver.template
	</~~source~~>		</syntaxhighlight>

	==Driver Linkage==		==Driver Linkage==

Connect to SQLite database (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:12:03 GMT

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	sudo apt-get install libsqlite3-0		sudo apt-get install libsqlite3-0
	sudo ln -s /usr/lib/x86_64-linux-gnu/libsqlite3.so.0 /usr/lib/x86_64-linux-gnu/libsqlite3.so		sudo ln -s /usr/lib/x86_64-linux-gnu/libsqlite3.so.0 /usr/lib/x86_64-linux-gnu/libsqlite3.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>		<li>
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	sudo yum install sqlite		sudo yum install sqlite
	sudo ln -s /usr/lib64/libsqlite3.so.0 /usr/lib64/libsqlite3.so		sudo ln -s /usr/lib64/libsqlite3.so.0 /usr/lib64/libsqlite3.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	</ol>		</ol>

Connect to PostgreSQL (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:12:01 GMT

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	[PG]		[PG]
	VendorLib=<folder>\libpq.dll		VendorLib=<folder>\libpq.dll
	</~~source~~>		</syntaxhighlight>

	If the PostgreSQL client library has not been installed properly, an exception is raised when you try to connect:		If the PostgreSQL client library has not been installed properly, an exception is raised when you try to connect:
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	sudo apt-get install libpq5		sudo apt-get install libpq5
	sudo ln -s /usr/lib/x86_64-linux-gnu/libpq.so.5 /usr/lib/x86_64-linux-gnu/libpq.so		sudo ln -s /usr/lib/x86_64-linux-gnu/libpq.so.5 /usr/lib/x86_64-linux-gnu/libpq.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>		<li>
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	sudo yum install postgresql-libs		sudo yum install postgresql-libs
	sudo ln -s /usr/lib64/libpq.so.5 /usr/lib64/libpq.so		sudo ln -s /usr/lib64/libpq.so.5 /usr/lib64/libpq.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	</ol>		</ol>
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	$body$		$body$
	LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;		LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;
	</~~source~~>		</syntaxhighlight>

	==Connection Definition Parameters==		==Connection Definition Parameters==

Connect to Oracle Server (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:12:00 GMT

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	Install the libaio library:		Install the libaio library:
	* On '''{{SupportedUbuntu}}''', run:		* On '''{{SupportedUbuntu}}''', run:
	*: <syntaxhighlight lang="bash" enclose="none">sudo apt-get install libaio1</~~source~~>		*: <syntaxhighlight lang="bash" enclose="none">sudo apt-get install libaio1</syntaxhighlight>
	* On '''{{SupportedRHEL}}''', run:		* On '''{{SupportedRHEL}}''', run:
	*: <syntaxhighlight lang="bash" enclose="none">sudo yum install libaio</~~source~~>		*: <syntaxhighlight lang="bash" enclose="none">sudo yum install libaio</syntaxhighlight>
	</li>		</li>
	<li>		<li>

Connect to MySQL Server (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:59 GMT

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	[MySQL]		[MySQL]
	VendorLib=<folder>\libmysql.dll		VendorLib=<folder>\libmysql.dll
	</~~source~~>		</syntaxhighlight>

	If the MySQL client library has not been installed properly, an exception is raised when you try to connect:		If the MySQL client library has not been installed properly, an exception is raised when you try to connect:
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	sudo apt-get install libmysqlclient20		sudo apt-get install libmysqlclient20
	sudo ln -s /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20 /usr/lib/x86_64-linux-gnu/libmysqlclient.so		sudo ln -s /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20 /usr/lib/x86_64-linux-gnu/libmysqlclient.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>		<li>
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	sudo yum install mysql-libs		sudo yum install mysql-libs
	sudo ln -s /usr/lib64/mysql/libmysqlclient.so.18 /usr/lib64/mysql/libmysqlclient.so		sudo ln -s /usr/lib64/mysql/libmysqlclient.so.18 /usr/lib64/mysql/libmysqlclient.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	</ol>		</ol>

Connect to MongoDB Database (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:57 GMT

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	[Mongo]		[Mongo]
	VendorLib=<folder>\libmongoc-1.0.dll		VendorLib=<folder>\libmongoc-1.0.dll
	</~~source~~>		</syntaxhighlight>

	If the MongoDB client library has not been properly installed, an exception is raised when you try to connect:		If the MongoDB client library has not been properly installed, an exception is raised when you try to connect:
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	sudo ln -s /usr/lib/x86_64-linux-gnu/libmongoc-1.0.so.0 /usr/lib/x86_64-linux-gnu/libmongoc-1.0.so		sudo ln -s /usr/lib/x86_64-linux-gnu/libmongoc-1.0.so.0 /usr/lib/x86_64-linux-gnu/libmongoc-1.0.so
	sudo ln -s /usr/lib/x86_64-linux-gnu/libbson-1.0.so.0 /usr/lib/x86_64-linux-gnu/libbson-1.0.so		sudo ln -s /usr/lib/x86_64-linux-gnu/libbson-1.0.so.0 /usr/lib/x86_64-linux-gnu/libbson-1.0.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>		<li>
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	sudo ln -s /usr/lib64/libmongoc-1.0.so.0 /usr/lib/x86_64-linux-gnu/libmongoc-1.0.so		sudo ln -s /usr/lib64/libmongoc-1.0.so.0 /usr/lib/x86_64-linux-gnu/libmongoc-1.0.so
	sudo ln -s /usr/lib64/libbson-1.0.so.0 /usr/lib/x86_64-linux-gnu/libbson-1.0.so		sudo ln -s /usr/lib64/libbson-1.0.so.0 /usr/lib/x86_64-linux-gnu/libbson-1.0.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	</ol>		</ol>

Connect to Microsoft SQL Server Compact Edition (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:57 GMT

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	DriverName="SQLServer Compact"		DriverName="SQLServer Compact"
	Database=c:\mydb.sdf		Database=c:\mydb.sdf
	</~~source~~>		</syntaxhighlight>

	* Drop TFDConnection to the form.		* Drop TFDConnection to the form.

Connect to Microsoft SQL Server (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:56 GMT

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	tar -xavf msodbcsql-11.0.2270.0.tar.gz		tar -xavf msodbcsql-11.0.2270.0.tar.gz
	sudo bash msodbcsql-11.0.2270.0/install.sh install --accept-license --force		sudo bash msodbcsql-11.0.2270.0/install.sh install --accept-license --force
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>		<li>

Connect to InterBase (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:56 GMT

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	[IB]		[IB]
	VendorLib=<folder>\gds32.dll		VendorLib=<folder>\gds32.dll
	</~~source~~>		</syntaxhighlight>

	If the InterBase client library has not been installed properly, an exception is raised when you try to connect:		If the InterBase client library has not been installed properly, an exception is raised when you try to connect:

Connect to IBM DB2 Server (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:55 GMT

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	echo Threading=1 >> db2.driver.template		echo Threading=1 >> db2.driver.template
	odbcinst -i -d -f db2.driver.template		odbcinst -i -d -f db2.driver.template
	</~~source~~>		</syntaxhighlight>

	==Driver Linkage==		==Driver Linkage==

Connect to Firebird (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:54 GMT

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← Older revision		Revision as of 18:11, 14 July 2026
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	[FB]		[FB]
	VendorLib=<folder>\fbclient.dll		VendorLib=<folder>\fbclient.dll
	</~~source~~>		</syntaxhighlight>

	If the Firebird client library has not been installed properly, an exception is raised when you try to connect:		If the Firebird client library has not been installed properly, an exception is raised when you try to connect:
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	sudo apt-get install libfbclient2		sudo apt-get install libfbclient2
	sudo ln -s /usr/lib/x86_64-linux-gnu/libfbclient.so.2 /usr/lib/x86_64-linux-gnu/libfbclient.so		sudo ln -s /usr/lib/x86_64-linux-gnu/libfbclient.so.2 /usr/lib/x86_64-linux-gnu/libfbclient.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>		<li>
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	sudo yum install firebird-libfbclient		sudo yum install firebird-libfbclient
	sudo ln -s /usr/lib64/libfbclient.so.2 /usr/lib64/libfbclient.so		sudo ln -s /usr/lib64/libfbclient.so.2 /usr/lib64/libfbclient.so
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	</ol>		</ol>

Connect to Advantage Database Server (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:54 GMT

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	[ADS]		[ADS]
	VendorLib=<folder>\ace32.dll		VendorLib=<folder>\ace32.dll
	</~~source~~>		</syntaxhighlight>

	If the ADS client library has not been installed properly, an exception is raised when you try to connect:		If the ADS client library has not been installed properly, an exception is raised when you try to connect:
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	cd aceapi-*		cd aceapi-*
	sudo ./setup.pl		sudo ./setup.pl
	</~~source~~>		</syntaxhighlight>

	==Driver Linkage==		==Driver Linkage==

Configuring Drivers (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:52 GMT

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	BaseDriverID=FB		BaseDriverID=FB
	VendorLib=C:\ib\fb21_embed\bin\fbembed.dll		VendorLib=C:\ib\fb21_embed\bin\fbembed.dll
	</~~source~~>		</syntaxhighlight>


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	FDConnection1.Connected := True;		FDConnection1.Connected := True;
	end;		end;
	</~~source~~>		</syntaxhighlight>

	When a connection using a driver has been established and an application needs to switch to the other DBMS client:		When a connection using a driver has been established and an application needs to switch to the other DBMS client:
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	FDPhysFBDriverLink1.VendorLib := 'C:\fbclient.dll';		FDPhysFBDriverLink1.VendorLib := 'C:\fbclient.dll';
	FDConnection1.Open;		FDConnection1.Open;
	</~~source~~>		</syntaxhighlight>

	<blockquote>'''Note''': Although it is possible to use link components to configure drivers at design time, we do not recommend it, because it is difficult to load a module with a link component before any other module with the FireDAC components is loaded. Therefore, the link component configures the driver properly.</blockquote>		<blockquote>'''Note''': Although it is possible to use link components to configure drivers at design time, we do not recommend it, because it is difficult to load a module with a link component before any other module with the FireDAC components is loaded. Therefore, the link component configures the driver properly.</blockquote>

Conditional compilation (Delphi)

WikiSysop — Tue, 14 Jul 2026 18:11:51 GMT

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	Writeln('Debug is off.'); // This code executes.		Writeln('Debug is off.'); // This code executes.
	{$ENDIF}		{$ENDIF}
	</~~source~~>		</syntaxhighlight>

	{{Note\|Conditional symbols are not {{Delphi}} identifiers and cannot be referenced in actual program code. Similarly, {{Delphi}} identifiers cannot be referenced in any conditional directives other than <code>{$IF}</code> and <code>{$ELSEIF}</code>.}}		{{Note\|Conditional symbols are not {{Delphi}} identifiers and cannot be referenced in actual program code. Similarly, {{Delphi}} identifiers cannot be referenced in any conditional directives other than <code>{$IF}</code> and <code>{$ELSEIF}</code>.}}
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	{$IFEND}		{$IFEND}
	{$ENDIF}		{$ENDIF}
	</~~source~~>		</syntaxhighlight>

	See the '''[[Compiler Versions\|table of Compiler Versions]]''' for a list of version numbers associated with various released {{Delphi}} compilers.		See the '''[[Compiler Versions\|table of Compiler Versions]]''' for a list of version numbers associated with various released {{Delphi}} compilers.

Compl

WikiSysop — Tue, 14 Jul 2026 18:11:51 GMT

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	return 0; // put breakpoint here to see the console output		return 0; // put breakpoint here to see the console output
	}		}
	</~~source~~>		</syntaxhighlight>
	===Console output===		===Console output===
	fffffffe		fffffffe

Compiling and Linking a macOS C++ Console Application from Command Line

WikiSysop — Tue, 14 Jul 2026 18:11:51 GMT

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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	This code creates and runs a POSIX thread.		This code creates and runs a POSIX thread.

Compiling a C++ Application from the Command Line

WikiSysop — Tue, 14 Jul 2026 18:11:50 GMT

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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>
	</li>		</li>
	<li>Create a batch file, '''Build.bat''', containing the command line copied from the '''Messages View'''. The paths in the .bat file might vary depending on where your IDE is installed and the host Windows platform. For example:		<li>Create a batch file, '''Build.bat''', containing the command line copied from the '''Messages View'''. The paths in the .bat file might vary depending on where your IDE is installed and the host Windows platform. For example:

Compiler Directives for Strings

WikiSysop — Tue, 14 Jul 2026 18:11:49 GMT

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	{{Code\|{$V+/-}\|}}		{{Code\|{$V+/-}\|}}
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	The {{Code\|$V}} directive controls type checking on short strings passed as variable parameters. In the {{Code\|{$V+}\|}} state, strict type checking is performed, requiring the formal and actual parameters to be of identical string types. In the {{Code\|{$V-}\|}} (relaxed) state, any short string type variable is allowed as an actual parameter, even if the declared maximum length is not the same as that of the formal parameter. Be aware that this could lead to memory corruption. For example: <syntaxhighlight lang="delphi" enclose="none">var S: string[3];</~~source~~>.		The {{Code\|$V}} directive controls type checking on short strings passed as variable parameters. In the {{Code\|{$V+}\|}} state, strict type checking is performed, requiring the formal and actual parameters to be of identical string types. In the {{Code\|{$V-}\|}} (relaxed) state, any short string type variable is allowed as an actual parameter, even if the declared maximum length is not the same as that of the formal parameter. Be aware that this could lead to memory corruption. For example: <syntaxhighlight lang="delphi" enclose="none">var S: string[3];</syntaxhighlight>.

	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
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	Test(S);		Test(S);
	end.		end.
	</~~source~~>		</syntaxhighlight>
	\|-		\|-
	\| align="left" valign="top" \|		\| align="left" valign="top" \|

Compiler Attributes

WikiSysop — Tue, 14 Jul 2026 18:11:49 GMT

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	[volatile] FMyVariable: TMyType;		[volatile] FMyVariable: TMyType;
	end;		end;
	</~~source~~>		</syntaxhighlight>

	== Weak ==		== Weak ==

Command Batches (FireDAC)

WikiSysop — Tue, 14 Jul 2026 18:11:48 GMT

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	FDQuery1.Open; // [Orders] table rows are accessable here		FDQuery1.Open; // [Orders] table rows are accessable here
	FDQuery1.NextRecordSet; // [Order Details] table rows available here		FDQuery1.NextRecordSet; // [Order Details] table rows available here
	</~~source~~>		</syntaxhighlight>

	An application can store each result set into a separate dataset, using the [[lib_en:FireDAC.Comp.Client.TFDMemTable\|TFDMemTable]] and [[lib_en:FireDAC.Comp.DataSet.TFDDataSet.Data\|Data]] property. For example:		An application can store each result set into a separate dataset, using the [[lib_en:FireDAC.Comp.Client.TFDMemTable\|TFDMemTable]] and [[lib_en:FireDAC.Comp.DataSet.TFDDataSet.Data\|Data]] property. For example:
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	// assign customers records to FDMemTable2		// assign customers records to FDMemTable2
	FDMemTable2.Data := FDQuery1.Data;		FDMemTable2.Data := FDQuery1.Data;
	</~~source~~>		</syntaxhighlight>

	FireDAC automatically skips empty result sets that do not have columns and rows.		FireDAC automatically skips empty result sets that do not have columns and rows.

Command-Line Interfaces of Clang-enhanced C++ Compilers

WikiSysop — Tue, 14 Jul 2026 18:11:47 GMT

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	* {{Code\|-I}} is for headers provided by third parties.		* {{Code\|-I}} is for headers provided by third parties.
	* {{Code\|-idirafter}} is for paths searched after paths specified via {{Code\|-I}} or {{Code\|-isystem}} have been searched. If the path has a leading '=' character, this character is replaced with the value specified via {{Code\|-sysroot}}.		* {{Code\|-idirafter}} is for paths searched after paths specified via {{Code\|-I}} or {{Code\|-isystem}} have been searched. If the path has a leading '=' character, this character is replaced with the value specified via {{Code\|-sysroot}}.
	* {{Code\|-iquote}} is for your own source files and headers. As the name suggests, this path is used only for directives with quotes: <syntaxhighlight lang="cpp" enclose="none">#include "file"</~~source~~>. If the named {{Path\|file}} is not found, then the paths specified by {{Code\|-I}} and {{Code\|-isystem}} are searched, as if the directive was <syntaxhighlight lang="cpp" enclose="none">#include <file></~~source~~>.		* {{Code\|-iquote}} is for your own source files and headers. As the name suggests, this path is used only for directives with quotes: <syntaxhighlight lang="cpp" enclose="none">#include "file"</syntaxhighlight>. If the named {{Path\|file}} is not found, then the paths specified by {{Code\|-I}} and {{Code\|-isystem}} are searched, as if the directive was <syntaxhighlight lang="cpp" enclose="none">#include <file></syntaxhighlight>.

	For more information, see [[include\|#include]].		For more information, see [[include\|#include]].

Coding responses to user actions in the Code Editor (IDE Tutorial)

WikiSysop — Tue, 14 Jul 2026 18:11:37 GMT

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Show changes

Code Completion

WikiSysop — Tue, 14 Jul 2026 18:11:36 GMT

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← Older revision		Revision as of 18:11, 14 July 2026
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	var		var
	GViewButtons: TObjectList<TToolButton>;		GViewButtons: TObjectList<TToolButton>;
	</~~source~~>		</syntaxhighlight>

	In your application, you need to do a <code>for</code> loop through the buttons in the collection, and you do not know how many buttons are in the collection. Your code block is similar to the following:		In your application, you need to do a <code>for</code> loop through the buttons in the collection, and you do not know how many buttons are in the collection. Your code block is similar to the following:
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	{ ... }		{ ... }
	end;		end;
	</~~source~~>		</syntaxhighlight>

	Move your cursor beyond the '''.''' (period character) after the <code>GViewButtons</code> statement, and press <code>Ctrl+Space</code>. The Code Completion window appears, as follows:		Move your cursor beyond the '''.''' (period character) after the <code>GViewButtons</code> statement, and press <code>Ctrl+Space</code>. The Code Completion window appears, as follows:
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	{ ... }		{ ... }
	end;		end;
	</~~source~~>		</syntaxhighlight>

	==Using Code Completion==		==Using Code Completion==

Closure

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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	However, you cannot assign a pointer to a member of a derived class to a pointer to a member of a base class. This rule (called contravariance) is illustrated in the following example:		However, you cannot assign a pointer to a member of a derived class to a pointer to a member of a base class. This rule (called contravariance) is illustrated in the following example:
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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	The __closure keyword extension allows you to skirt this limitation, and more. Using a closure, you can get a pointer to member function for an object (for example, a particular instance of a class). The object can be any object, regardless of its inheritance hierarchy. The pointer of the object is automatically used when calling the member function through the closure. The following example shows how to declare and use a closure. The base and derived classes provided earlier are assumed to be defined.		The __closure keyword extension allows you to skirt this limitation, and more. Using a closure, you can get a pointer to member function for an object (for example, a particular instance of a class). The object can be any object, regardless of its inheritance hierarchy. The pointer of the object is automatically used when calling the member function through the closure. The following example shows how to declare and use a closure. The base and derived classes provided earlier are assumed to be defined.
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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	For a code example, see [[samp_xe:TRegExReplace (C++)\|TRegExReplace (C++)]].		For a code example, see [[samp_xe:TRegExReplace (C++)\|TRegExReplace (C++)]].
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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	Notice that we are passing a pointer to an instance of the derived class, and we are using it to get a pointer to a member function in the base class--something standard C++ does not allow us to do.		Notice that we are passing a pointer to an instance of the derived class, and we are using it to get a pointer to a member function in the base class--something standard C++ does not allow us to do.

Clear87, clearfp

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	unsigned int _clear87 (void);		unsigned int _clear87 (void);
	unsigned int _clearfp (void);		unsigned int _clearfp (void);
	</~~source~~>		</syntaxhighlight>

	==Description==		==Description==
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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	[[Category:C++ Reference]]		[[Category:C++ Reference]]

Classmethod

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	virtual __classmethod int FUNCTION_NAME(int );		virtual __classmethod int FUNCTION_NAME(int );
	__classmethod virtual int FUNCTION_NAME(int );		__classmethod virtual int FUNCTION_NAME(int );
	</~~source~~>		</syntaxhighlight>

	==Description==		==Description==

Classid

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	}		}
	}		}
	</~~source~~>		</syntaxhighlight>

	==See Also==		==See Also==

Classes and Objects (Delphi)

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	memberList		memberList
	end;		end;
	</~~source~~>		</syntaxhighlight>

	'''Required elements of the class type declaration'''		'''Required elements of the class type declaration'''
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	function Write(const Buffer: TBytes; Offset, Count: Longint): Longint; override;		function Write(const Buffer: TBytes; Offset, Count: Longint): Longint; override;
	end; // deprecated 'Use TBytesStream';		end; // deprecated 'Use TBytesStream';
	</~~source~~>		</syntaxhighlight>

	<code>Classes.TMemoryStream</code> descends from <code>Classes.TCustomMemoryStream</code>, inheriting most of its members. But it defines – or redefines – several methods and properties, including its destructor method, <code>Destroy</code>. Its constructor, <code>Create</code>, is inherited without change from <code>System.TObject</code>, and so is not redeclared. Each member is declared as '''private''', '''protected''', or '''public''' (this class has no '''published''' members). These terms are explained below.		<code>Classes.TMemoryStream</code> descends from <code>Classes.TCustomMemoryStream</code>, inheriting most of its members. But it defines – or redefines – several methods and properties, including its destructor method, <code>Destroy</code>. Its constructor, <code>Create</code>, is inherited without change from <code>System.TObject</code>, and so is not redeclared. Each member is declared as '''private''', '''protected''', or '''public''' (this class has no '''published''' members). These terms are explained below.
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	begin		begin
	stream := TMemoryStream.Create;		stream := TMemoryStream.Create;
	</~~source~~>		</syntaxhighlight>

	== Inheritance and Scope ==		== Inheritance and Scope ==
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	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	type TSomeControl = class(TControl);		type TSomeControl = class(TControl);
	</~~source~~>		</syntaxhighlight>

	declares a class called <span class="codeInline">TSomeControl</span> that descends from <!--Borland.VCL.-->{{f\|radstudio\|[[lib_en:Vcl.Controls.TControl\|Vcl.Controls.TControl]]}}{{f\|appmethod\|[[lib_en:FMX.Controls.TControl\|FMX.Controls.TControl]]}}. A class type automatically inherits all of the members from its immediate ancestor. Each class can declare new members and can redefine inherited ones, but a class cannot remove members defined in an ancestor. Hence <span class="codeInline">TSomeControl</span> contains all of the members defined in <!--Borland.VCL.-->{{f\|radstudio\|[[lib_en:Vcl.Controls.TControl\|Vcl.Controls.TControl]]}}{{f\|appmethod\|[[lib_en:FMX.Controls.TControl\|FMX.Controls.TControl]]}} and in each of the <!--Borland.VCL.-->{{f\|radstudio\|[[lib_en:Vcl.Controls.TControl\|Vcl.Controls.TControl]]}}{{f\|appmethod\|[[lib_en:FMX.Controls.TControl\|FMX.Controls.TControl]]}} ancestors.		declares a class called <span class="codeInline">TSomeControl</span> that descends from <!--Borland.VCL.-->{{f\|radstudio\|[[lib_en:Vcl.Controls.TControl\|Vcl.Controls.TControl]]}}{{f\|appmethod\|[[lib_en:FMX.Controls.TControl\|FMX.Controls.TControl]]}}. A class type automatically inherits all of the members from its immediate ancestor. Each class can declare new members and can redefine inherited ones, but a class cannot remove members defined in an ancestor. Hence <span class="codeInline">TSomeControl</span> contains all of the members defined in <!--Borland.VCL.-->{{f\|radstudio\|[[lib_en:Vcl.Controls.TControl\|Vcl.Controls.TControl]]}}{{f\|appmethod\|[[lib_en:FMX.Controls.TControl\|FMX.Controls.TControl]]}} and in each of the <!--Borland.VCL.-->{{f\|radstudio\|[[lib_en:Vcl.Controls.TControl\|Vcl.Controls.TControl]]}}{{f\|appmethod\|[[lib_en:FMX.Controls.TControl\|FMX.Controls.TControl]]}} ancestors.
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	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	TClass = class of TObject;		TClass = class of TObject;
	</~~source~~>		</syntaxhighlight>

	If the declaration of a class type does not specify an ancestor, the class inherits directly from <!--Borland.Delphi.-->[[lib_en:System.TObject\|System.TObject]]. Thus:		If the declaration of a class type does not specify an ancestor, the class inherits directly from <!--Borland.Delphi.-->[[lib_en:System.TObject\|System.TObject]]. Thus:
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	var		var
	Fig: TFigure;		Fig: TFigure;
	</~~source~~>		</syntaxhighlight>

	the variable <span class="codeInline">Fig</span> can be assigned values of type <span class="codeInline">TFigure</span>, <span class="codeInline">TRectangle</span>, and <span class="codeInline">TSquare</span>.		the variable <span class="codeInline">Fig</span> can be assigned values of type <span class="codeInline">TFigure</span>, <span class="codeInline">TRectangle</span>, and <span class="codeInline">TSquare</span>.
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	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	published property Color: TColor read GetColor write SetColor;		published property Color: TColor read GetColor write SetColor;
	</~~source~~>		</syntaxhighlight>

	declares a published property called <span class="codeInline">Color</span>. Visibility determines where and how a member can be accessed, with '''private''' representing the least accessibility, '''protected''' representing an intermediate level of accessibility, and '''public''', '''published''', and automated representing the greatest accessibility.		declares a published property called <span class="codeInline">Color</span>. Visibility determines where and how a member can be accessed, with '''private''' representing the least accessibility, '''protected''' representing an intermediate level of accessibility, and '''public''', '''published''', and automated representing the greatest accessibility.
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	{ published declarations here }		{ published declarations here }
	end;		end;
	</~~source~~>		</syntaxhighlight>

	You can increase the visibility of a property in a descendent class by redeclaring it, but you cannot decrease its visibility. For example, a '''protected''' property can be made '''public''' in a descendant, but not '''private'''. Moreover, '''published''' properties cannot become '''public''' in a descendent class. For more information, see [[Properties (Delphi)\|Property Overrides and Redeclarations]].		You can increase the visibility of a property in a descendent class by redeclaring it, but you cannot decrease its visibility. For example, a '''protected''' property can be made '''public''' in a descendant, but not '''private'''. Moreover, '''published''' properties cannot become '''public''' in a descendent class. For more information, see [[Properties (Delphi)\|Property Overrides and Redeclarations]].
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	// ...		// ...
	end;		end;
	</~~source~~>		</syntaxhighlight>

	Do not confuse forward declarations with complete declarations of types that derive from <!--Borland.Delphi.-->[[lib_en:System.TObject\|System.TObject]] without declaring any class members.		Do not confuse forward declarations with complete declarations of types that derive from <!--Borland.Delphi.-->[[lib_en:System.TObject\|System.TObject]] without declaring any class members.
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	end; //		end; //
	TThirdClass = class(TObject); // this is a complete class declaration		TThirdClass = class(TObject); // this is a complete class declaration
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

Class and Record Helpers (Delphi)

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	X.HelloWorld; // Calls TMyClassHelper.HelloWorld		X.HelloWorld; // Calls TMyClassHelper.HelloWorld
	X.MyFunc; // Calls TMyClassHelper.MyFunc		X.MyFunc; // Calls TMyClassHelper.MyFunc
	</~~source~~>		</syntaxhighlight>

	Note that the class helper function <span class="codeInline">MyFunc</span> is called, because the class helper takes precedence over the actual class type.		Note that the class helper function <span class="codeInline">MyFunc</span> is called, because the class helper takes precedence over the actual class type.

Class Variable in Generics

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	Writeln(TFoo<String>.FCount); // outputs 1		Writeln(TFoo<String>.FCount); // outputs 1
	end.		end.
	</~~source~~>		</syntaxhighlight>
	== See Also ==		== See Also ==

Class References

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	type TClass = class of TObject;		type TClass = class of TObject;
	var AnyObj: TClass;		var AnyObj: TClass;
	</~~source~~>		</syntaxhighlight>

	declares a variable called <span class="codeInline">AnyObj</span> that can hold a reference to any class. (The definition of a class-reference type cannot occur directly in a variable declaration or parameter list.) You can assign the value '''nil''' to a variable of any class-reference type.		declares a variable called <span class="codeInline">AnyObj</span> that can hold a reference to any class. (The definition of a class-reference type cannot occur directly in a variable declaration or parameter list.) You can assign the value '''nil''' to a variable of any class-reference type.
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	...		...
	constructor Create(ItemClass: TCollectionItemClass);		constructor Create(ItemClass: TCollectionItemClass);
	</~~source~~>		</syntaxhighlight>
	This declaration says that to create a '''[[lib_en:System.Classes.TCollection\|TCollection]]''' instance object, you must pass to the constructor the name of a class descending from '''[[lib_en:System.Classes.TCollectionItem\|TCollectionItem]]'''.		This declaration says that to create a '''[[lib_en:System.Classes.TCollection\|TCollection]]''' instance object, you must pass to the constructor the name of a class descending from '''[[lib_en:System.Classes.TCollectionItem\|TCollectionItem]]'''.

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	end;		end;
	end;		end;
	</~~source~~>		</syntaxhighlight>

	The <span class="codeInline">CreateControl</span> function requires a class-reference parameter to tell it what kind of control to create. It uses this parameter to call the constructor of the class. Because class-type identifiers denote class-reference values, a call to <span class="codeInline">CreateControl</span> can specify the identifier of the class to create an instance of. For example:		The <span class="codeInline">CreateControl</span> function requires a class-reference parameter to tell it what kind of control to create. It uses this parameter to call the constructor of the class. Because class-type identifiers denote class-reference values, a call to <span class="codeInline">CreateControl</span> can specify the identifier of the class to create an instance of. For example:
	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	CreateControl(TEdit, 'Edit1', 10, 10, 100, 20);		CreateControl(TEdit, 'Edit1', 10, 10, 100, 20);
	</~~source~~>		</syntaxhighlight>
	Constructors called using class references are usually virtual. The constructor implementation activated by the call depends on the runtime type of the class reference.		Constructors called using class references are usually virtual. The constructor implementation activated by the call depends on the runtime type of the class reference.

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	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	if ActiveControl is TEdit then TEdit(ActiveControl).SelectAll;		if ActiveControl is TEdit then TEdit(ActiveControl).SelectAll;
	</~~source~~>		</syntaxhighlight>

	This statement casts the <code>ActiveControl</code> variable to the <span class="codeInline">TEdit</span> type. First it verifies that the object referenced by <code>ActiveControl</code> is an instance of <code>TEdit</code> or one of its descendants.		This statement casts the <code>ActiveControl</code> variable to the <span class="codeInline">TEdit</span> type. First it verifies that the object referenced by <code>ActiveControl</code> is an instance of <code>TEdit</code> or one of its descendants.
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	OnClick := OkClick;		OnClick := OkClick;
	end;		end;
	</~~source~~>		</syntaxhighlight>

	The rules of operator precedence often require '''as''' typecasts to be enclosed in parentheses. For example:		The rules of operator precedence often require '''as''' typecasts to be enclosed in parentheses. For example:
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	<syntaxhighlight lang="delphi">		<syntaxhighlight lang="delphi">
	(Sender as TButton).Caption := '&Ok';		(Sender as TButton).Caption := '&Ok';
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

Class Name Scope

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	S(&s); // OK: this is a function call		S(&s); // OK: this is a function call
	}		}
	</~~source~~>		</syntaxhighlight>

	C++ also allows a forward class declaration:		C++ also allows a forward class declaration:
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	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	class X; // no members, yet!		class X; // no members, yet!
	</~~source~~>		</syntaxhighlight>

	Forward declarations permit certain references to class name X (usually references to pointers to class objects) before the class has been fully defined. See Structure member declarations for more information. Of course, you must make a complete class declaration with members before you can define and use objects of that class.		Forward declarations permit certain references to class name X (usually references to pointers to class objects) before the class has been fully defined. See Structure member declarations for more information. Of course, you must make a complete class declaration with members before you can define and use objects of that class.

Class Methods

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	// Function that takes a class reference		// Function that takes a class reference
	function RegisterTestType(Cls: TTestClass): boolean;		function RegisterTestType(Cls: TTestClass): boolean;
	</~~source~~>		</syntaxhighlight>

	== Class Methods as Static Methods with Explicit TMetaClass* Parameter ==		== Class Methods as Static Methods with Explicit TMetaClass* Parameter ==
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	extern PACKAGE bool __fastcall RegisterTestType(TMetaClass* Cls);		extern PACKAGE bool __fastcall RegisterTestType(TMetaClass* Cls);
	</~~source~~>		</syntaxhighlight>

	There are several limitations with this way of exposing class methods using an explicit TMetaClass* parameter:		There are several limitations with this way of exposing class methods using an explicit TMetaClass* parameter:
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	__property UnicodeString StrProp = {read=GetStrProp, write=SetStrProp};		__property UnicodeString StrProp = {read=GetStrProp, write=SetStrProp};
	};		};
	</~~source~~>		</syntaxhighlight>

	{{CBuilder}} does not provide for a way to declare a class reference other than by T<span class="codeInline">MetaClass*</span>. Hence, class methods are invoked with a typename or with an instance of a object. Virtual class methods are invoked the same way regular virtual methods are invoked, except that instead of the this pointer being pushed, the metaclass pointer is the hidden parameter.		{{CBuilder}} does not provide for a way to declare a class reference other than by T<span class="codeInline">MetaClass*</span>. Hence, class methods are invoked with a typename or with an instance of a object. Virtual class methods are invoked the same way regular virtual methods are invoked, except that instead of the this pointer being pushed, the metaclass pointer is the hidden parameter.
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	TDerived::cfunc(); //calls version in TDerived--compile time--not dynamic		TDerived::cfunc(); //calls version in TDerived--compile time--not dynamic
	__classid(TDerived)->cfunc(); //compiler error		__classid(TDerived)->cfunc(); //compiler error
	</~~source~~>		</syntaxhighlight>

	=== Updating Your Code to Use __classmethod ===		=== Updating Your Code to Use __classmethod ===
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	static int __fastcall add(TMetaClass* vmt, int I, int J);		static int __fastcall add(TMetaClass* vmt, int I, int J);
	};		};
	</~~source~~>		</syntaxhighlight>
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
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	__classmethod int __fastcall add(int I, int J);		__classmethod int __fastcall add(int I, int J);
	};		};
	</~~source~~>		</syntaxhighlight>
	\|-		\|-
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
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	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	TTest::add(__classid(TTest), 10, 20);		TTest::add(__classid(TTest), 10, 20);
	</~~source~~>		</syntaxhighlight>
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	TTest::add(10, 20);		TTest::add(10, 20);
	</~~source~~>		</syntaxhighlight>
	\|-		\|-
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
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	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	TTestDerived::add(__classid(TTestDerived), 10, 20);		TTestDerived::add(__classid(TTestDerived), 10, 20);
	</~~source~~>		</syntaxhighlight>
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	TTestDerived::add(10, 20);		TTestDerived::add(10, 20);
	</~~source~~>		</syntaxhighlight>
	\|-		\|-
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
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	// …		// …
	TTest::add(p->ClassType(), 10, 20);		TTest::add(p->ClassType(), 10, 20);
	</~~source~~>		</syntaxhighlight>
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
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	// …		// …
	p->add(10, 20);		p->add(10, 20);
	</~~source~~>		</syntaxhighlight>
	\|-		\|-
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
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	// …		// …
	TTest::add(p->ClassType(), 10, 20);		TTest::add(p->ClassType(), 10, 20);
	</~~source~~>		</syntaxhighlight>
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
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	// …		// …
	p->add(10, 20);		p->add(10, 20);
	</~~source~~>		</syntaxhighlight>
	\|-		\|-
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
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	// …		// …
	p->Count = 20;		p->Count = 20;
	</~~source~~>		</syntaxhighlight>
	\| align="left" valign="top" \|		\| align="left" valign="top" \|
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
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	// …		// …
	p->Count = 20;		p->Count = 20;
	</~~source~~>		</syntaxhighlight>
	\|}		\|}

Class Initialization

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	X five(two); // calls X::X(const X&)		X five(two); // calls X::X(const X&)
	}		}
	</~~source~~>		</syntaxhighlight>

	The constructor can assign values to its members in two ways:		The constructor can assign values to its members in two ways:
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	X(int i, int j) { a = i; b = j }		X(int i, int j) { a = i; b = j }
	};		};
	</~~source~~>		</syntaxhighlight>

	2. An initializer list can be used prior to the function body:		2. An initializer list can be used prior to the function body:
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	X(int i, int j) : a(i), b(j), c(a) {}		X(int i, int j) : a(i), b(j), c(a) {}
	};		};
	</~~source~~>		</syntaxhighlight>

	The initializer list is the only place to initialize a reference variable.		The initializer list is the only place to initialize a reference variable.
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	top(int i, int j) : base1(i*5), base2(j+i), a(i) { b = j;}		top(int i, int j) : base1(i*5), base2(j+i), a(i) { b = j;}
	};		};
	</~~source~~>		</syntaxhighlight>

	With this class hierarchy, a declaration of top one(1, 2) would result in the initialization of base1 with the value 5 and base2 with the value 3. The methods of initialization can be intermixed.		With this class hierarchy, a declaration of top one(1, 2) would result in the initialization of base1 with the value 5 and base2 with the value 3. The methods of initialization can be intermixed.
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	X(int i, j) : a(i), b(a+j) {}		X(int i, j) : a(i), b(a+j) {}
	};		};
	</~~source~~>		</syntaxhighlight>

	With this class, a declaration of X x(1,1) results in an assignment of 1 to x::a and 2 to x::b.		With this class, a declaration of X x(1,1) results in an assignment of 1 to x::a and 2 to x::b.
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	derived(int i) : a(i*10), base(a) { } // Watch out! Base will be		derived(int i) : a(i*10), base(a) { } // Watch out! Base will be
	// passed an uninitialized 'a' };		// passed an uninitialized 'a' };
	</~~source~~>		</syntaxhighlight>

	With this class setup, a call of derived d(1) will not result in a value of 10 for the base class member x. The value passed to the base class constructor will be undefined.		With this class setup, a call of derived d(1) will not result in a value of 10 for the base class member x. The value passed to the base class constructor will be undefined.
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	// …		// …
	}		}
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

ClassGroup pseudo-property of TDataModule

WikiSysop — Tue, 14 Jul 2026 18:11:19 GMT

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	'''{{Delphi}}:'''		'''{{Delphi}}:'''
	<syntaxhighlight lang='delphi'> {%CLASSGROUP 'System.Classes.TPersistent'} </~~source~~>		<syntaxhighlight lang='delphi'> {%CLASSGROUP 'System.Classes.TPersistent'} </syntaxhighlight>

	'''C++:'''		'''C++:'''
	<syntaxhighlight lang='cpp'> #pragma classgroup "System.Classes.TPersistent" </~~source~~>		<syntaxhighlight lang='cpp'> #pragma classgroup "System.Classes.TPersistent" </syntaxhighlight>

	{{Note\| This directive is used only by the IDE and indicates the data module's relationship with a particular component framework, if any. Then the IDE enforces the kinds of components that you can drop on the data module. <br>		{{Note\| This directive is used only by the IDE and indicates the data module's relationship with a particular component framework, if any. Then the IDE enforces the kinds of components that you can drop on the data module. <br>

Clang-enhanced C++ Compilers

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	* Clang-enhanced C++ compilers allow a default argument only in a function declaration.		* Clang-enhanced C++ compilers allow a default argument only in a function declaration.
	*: Previous-generation C++ compilers allow default arguments in a function pointer or closure declaration as well.		*: Previous-generation C++ compilers allow default arguments in a function pointer or closure declaration as well.
	* Clang-enhanced C++ compilers do not allow the use of [[sizeof]] in a preprocessor directive, such as <syntaxhighlight lang="cpp" enclose="none">#if sizeof(ATypeName) > 20</~~source~~>.		* Clang-enhanced C++ compilers do not allow the use of [[sizeof]] in a preprocessor directive, such as <syntaxhighlight lang="cpp" enclose="none">#if sizeof(ATypeName) > 20</syntaxhighlight>.
	* Clang-enhanced C++ compilers are stricter about conversions.		* Clang-enhanced C++ compilers are stricter about conversions.
	: For example, converting string constants to <syntaxhighlight lang="cpp" enclose="none">char </~~source~~> generates a warning (conversion from string literal to <syntaxhighlight lang="cpp" enclose="none">char </~~source~~> is deprecated). On the other hand, initializing a <syntaxhighlight lang="cpp" enclose="none">char </~~source~~> with an <syntaxhighlight lang="cpp" enclose="none">unsigned char </~~source~~> results in a plain error (Cannot initialize a variable of type 'char ' with an rvalue of type <syntaxhighlight lang="cpp" enclose="none">BYTE </~~source~~>, also known as <syntaxhighlight lang="cpp" enclose="none">unsigned char </~~source~~>).		: For example, converting string constants to <syntaxhighlight lang="cpp" enclose="none">char </syntaxhighlight> generates a warning (conversion from string literal to <syntaxhighlight lang="cpp" enclose="none">char </syntaxhighlight> is deprecated). On the other hand, initializing a <syntaxhighlight lang="cpp" enclose="none">char </syntaxhighlight> with an <syntaxhighlight lang="cpp" enclose="none">unsigned char </syntaxhighlight> results in a plain error (Cannot initialize a variable of type 'char ' with an rvalue of type <syntaxhighlight lang="cpp" enclose="none">BYTE </syntaxhighlight>, also known as <syntaxhighlight lang="cpp" enclose="none">unsigned char </syntaxhighlight>).
	* Clang-enhanced C++ compilers do not allow you to mix <syntaxhighlight lang="cpp" enclose="none">__try</~~source~~> with <syntaxhighlight lang="cpp" enclose="none">catch</~~source~~>: this is because <syntaxhighlight lang="cpp" enclose="none">catch</~~source~~> must be used with <syntaxhighlight lang="cpp" enclose="none">try</~~source~~>; and <syntaxhighlight lang="cpp" enclose="none">__try</~~source~~> must be used with <syntaxhighlight lang="cpp" enclose="none">__except</~~source~~> and/or <syntaxhighlight lang="cpp" enclose="none">__finally</~~source~~>.		* Clang-enhanced C++ compilers do not allow you to mix <syntaxhighlight lang="cpp" enclose="none">__try</syntaxhighlight> with <syntaxhighlight lang="cpp" enclose="none">catch</syntaxhighlight>: this is because <syntaxhighlight lang="cpp" enclose="none">catch</syntaxhighlight> must be used with <syntaxhighlight lang="cpp" enclose="none">try</syntaxhighlight>; and <syntaxhighlight lang="cpp" enclose="none">__try</syntaxhighlight> must be used with <syntaxhighlight lang="cpp" enclose="none">__except</syntaxhighlight> and/or <syntaxhighlight lang="cpp" enclose="none">__finally</syntaxhighlight>.
	* Unicode identifiers are not supported by Clang-enhanced C++ compilers.		* Unicode identifiers are not supported by Clang-enhanced C++ compilers.
	* [[CPP32.EXE, the C Compiler Preprocessor\|CPP32]] supports the <syntaxhighlight lang="cpp" enclose="none">-Hp</~~source~~> option and prints header guard information that is used by the [[Precompiled Header Wizard]].		* [[CPP32.EXE, the C Compiler Preprocessor\|CPP32]] supports the <syntaxhighlight lang="cpp" enclose="none">-Hp</syntaxhighlight> option and prints header guard information that is used by the [[Precompiled Header Wizard]].
	* The Unix-style <syntaxhighlight lang="cpp" enclose="none">#line</~~source~~> is not the default <syntaxhighlight lang="cpp" enclose="none">#line</~~source~~> of CPP32, and so forth.		* The Unix-style <syntaxhighlight lang="cpp" enclose="none">#line</syntaxhighlight> is not the default <syntaxhighlight lang="cpp" enclose="none">#line</syntaxhighlight> of CPP32, and so forth.
	* Clang-enhanced C++ compilers do not support the [[final (C++)\|final]], [[deprecated]] and [[noreturn]] C++11 attributes. See [[Workaround for C++11 Attributes (Clang-enhanced C++ Compilers)\|Workaround for C++11 attributes]] for a workaround in Clang-enhanced C++ compilers.		* Clang-enhanced C++ compilers do not support the [[final (C++)\|final]], [[deprecated]] and [[noreturn]] C++11 attributes. See [[Workaround for C++11 Attributes (Clang-enhanced C++ Compilers)\|Workaround for C++11 attributes]] for a workaround in Clang-enhanced C++ compilers.
	* Many options of previous-generation C++ compilers are not supported by Clang-enhanced C++ compilers, and vice versa:		* Many options of previous-generation C++ compilers are not supported by Clang-enhanced C++ compilers, and vice versa:

Chsize

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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	'''Portability'''		'''Portability'''

Choosing Navigator Buttons to Display

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	end;		end;
	end;		end;
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

Chmod, wchmod

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	exit(0);		exit(0);
	}		}
	</~~source~~>		</syntaxhighlight>

	'''Portability'''		'''Portability'''

Chgsign, chgsignl

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	double _chgsign(double d);		double _chgsign(double d);
	long double _chgsignl(long double ld);		long double _chgsignl(long double ld);
	</~~source~~>		</syntaxhighlight>

	==Description==		==Description==
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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	[[Category:C++ Reference]]		[[Category:C++ Reference]]

Checking for Termination by Other Threads

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	PerformSomeTask;		PerformSomeTask;
	end;		end;
	</~~source~~>		</syntaxhighlight>
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	void __fastcall TMyThread::Execute() {		void __fastcall TMyThread::Execute() {
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	PerformSomeTask();		PerformSomeTask();
	}		}
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

Chdrive

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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	'''Portability'''		'''Portability'''

Chdir

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	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	chdir("a:\\BC");		chdir("a:\\BC");
	</~~source~~>		</syntaxhighlight>

	but this method changes only the current directory on that drive; it does not change the active drive.		but this method changes only the current directory on that drive; it does not change the active drive.
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	return 0;		return 0;
	}		}
	</~~source~~>		</syntaxhighlight>

	'''Portability'''		'''Portability'''

Character Constants

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	printf("\nSizeof wchar_t = %d", sizeof(wchar_t) );		printf("\nSizeof wchar_t = %d", sizeof(wchar_t) );
	}		}
	</~~source~~>		</syntaxhighlight>

	<blockquote>'''Note:''' Sizes are in bytes.</blockquote>		<blockquote>'''Note:''' Sizes are in bytes.</blockquote>

Char32 t

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	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	char32_t identifier;		char32_t identifier;
	</~~source~~>		</syntaxhighlight>

	'''Description'''		'''Description'''

Char16 t

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	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	char16_t identifier;		char16_t identifier;
	</~~source~~>		</syntaxhighlight>

	'''Description'''		'''Description'''

Changing the Tool with Speed Buttons

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	DrawingTool := dtRoundRect;		DrawingTool := dtRoundRect;
	end;		end;
	</~~source~~>		</syntaxhighlight>
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	void __fastcall TForm1::LineButtonClick(TObject * Sender)		void __fastcall TForm1::LineButtonClick(TObject * Sender)
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	DrawingTool = dtRoundRect;		DrawingTool = dtRoundRect;
	}		}
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

Changing the Pen Width

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	PenSize.Caption := IntToStr(PenWidth.Position); { convert to string for caption }		PenSize.Caption := IntToStr(PenWidth.Position); { convert to string for caption }
	end;		end;
	</~~source~~>		</syntaxhighlight>
	<syntaxhighlight lang="cpp">		<syntaxhighlight lang="cpp">
	void __fastcall TForm1::PenWidthChange(TObject *Sender) {		void __fastcall TForm1::PenWidthChange(TObject *Sender) {
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	PenSize->Caption = IntToStr(PenWidth->Position); // convert to string		PenSize->Caption = IntToStr(PenWidth->Position); // convert to string
	}		}
	</~~source~~>		</syntaxhighlight>

	== See Also ==		== See Also ==

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	* {{Code\|-I}} is for headers provided by third parties.		* {{Code\|-I}} is for headers provided by third parties.
	* {{Code\|-idirafter}} is for paths searched after paths specified via {{Code\|-I}} or {{Code\|-isystem}} have been searched. If the path has a leading '=' character, this character is replaced with the value specified via {{Code\|-sysroot}}.		* {{Code\|-idirafter}} is for paths searched after paths specified via {{Code\|-I}} or {{Code\|-isystem}} have been searched. If the path has a leading '=' character, this character is replaced with the value specified via {{Code\|-sysroot}}.
	* {{Code\|-iquote}} is for your own source files and headers. As the name suggests, this path is used only for directives with quotes: <syntaxhighlight lang="cpp" enclose="none">#include "file"</~~source~~>. If the named {{Path\|file}} is not found, then the paths specified by {{Code\|-I}} and {{Code\|-isystem}} are searched, as if the directive was <syntaxhighlight lang="cpp" enclose="none">#include <file></~~source~~>.		* {{Code\|-iquote}} is for your own source files and headers. As the name suggests, this path is used only for directives with quotes: <syntaxhighlight lang="cpp" enclose="none">#include "file"</syntaxhighlight>. If the named {{Path\|file}} is not found, then the paths specified by {{Code\|-I}} and {{Code\|-isystem}} are searched, as if the directive was <syntaxhighlight lang="cpp" enclose="none">#include <file></syntaxhighlight>.

	For more information, see [[include\|#include]].		For more information, see [[include\|#include]].