The Entire Project and Observing the Results

Go Up to Tutorial: Using LiveBinding Programatically

Caution: The programmatic method described here is NOT the standard way to implement binding expressions. Typically, you would use the Object Inspector (the standard method) in a VCL or an FMX application. You might never need to use the programmatic way of creating binding expressions. This tutorial demonstrates, however, that it is possible to manually create such expressions.

For examples of using LiveBindings in the standard way, see Tutorial: Using LiveBinding in VCL Applications and Tutorial: Using LiveBinding to Create a FireMonkey Application Without Code.

This topic contains the entire listing of the project and also the interpretation of the console output results.

The project listing

program LiveBindingProgr;
 
{$APPTYPE CONSOLE}
 
{$R *.res}
 
uses
  System.SysUtils,
  System.Bindings.Expression,
  System.Bindings.ObjEval,
  System.Bindings.Helper;
 
type
  TMyObject1 = class(TObject)
  private
    FIntegerValue: Integer;
    FStringValue: String;
  public
    property IntegerValue: Integer read FIntegerValue write FIntegerValue;
    property StringValue: String read FStringValue write FStringValue;
  end;
 
  TMyObject2 = class(TObject)
  private
    FIntegerValue: Integer;
    FStringValue: String;
  public
    property IntegerValue: Integer read FIntegerValue write FIntegerValue;
    property StringValue: String read FStringValue write FStringValue;
  end;
 
  TMyResultObject = class(TObject)
  private
    FIntegerValue: Integer;
    FStringValue: String;
  public
    property IntegerValue: Integer read FIntegerValue write FIntegerValue;
    property StringValue: String read FStringValue write FStringValue;
  end;
 
var
  MyObject1: TMyObject1;
  MyObject2: TMyObject2;
  MyResultObject: TMyResultObject;
 
  BindingExpression1: TBindingExpression;
  BindingExpression2: TBindingExpression;
 
begin
  MyObject1 := TMyObject1.Create;
  MyObject2 := TMyObject2.Create;
  MyResultObject := TMyResultObject.Create;
  try
    MyObject1.IntegerValue := 1;
    MyObject1.StringValue := 'LiveBinding ';
 
    MyObject2.IntegerValue := 2;
    MyObject2.StringValue := 'power.';
 
    { a binding expression that binds the two Integer properties of the given objects }
    BindingExpression1 := TBindings.CreateManagedBinding(
      { inputs }
      [TBindings.CreateAssociationScope([
        Associate(MyObject1, 'o1'),
        Associate(MyObject2, 'o2')
        ])],
      'o1.IntegerValue + o2.IntegerValue',
      { outputs }
      [TBindings.CreateAssociationScope([
        Associate(MyResultObject, 'res')
        ])],
      'res.IntegerValue',
      nil);
 
    { a binding expression that binds the two String properties of the given objects }
    BindingExpression2 := TBindings.CreateManagedBinding(
      { inputs }
      [TBindings.CreateAssociationScope([
        Associate(MyObject1, 'o1'),
        Associate(MyObject2, 'o2')
        ])],
      'o1.StringValue + o2.StringValue',
      { outputs }
      [TBindings.CreateAssociationScope([
        Associate(MyResultObject, 'res')
        ])],
      'res.StringValue',
      nil);
 
    TBindings.Notify(MyObject1, 'IntegerValue');
    TBindings.Notify(MyObject1, 'StringValue');
 
    Writeln('Result of add operation: ', MyResultObject.IntegerValue);
    Writeln(MyResultObject.StringValue);
    Readln;
  finally
    MyObject1.Free;
    MyObject2.Free;
    MyResultObject.Free;
  end;
end.

Tip: When you create the C++Builder Console Application, be sure to choose the Visual Component Library as Target Framework for the project to compile and link correctly.

#pragma hdrstop
#pragma argsused
#pragma explicit_rtti methods()
 
#include <tchar.h>
#include <stdio.h>
 
#include <System.Bindings.Expression.hpp>
#include <System.Bindings.Helper.hpp>
 
class TMyObject1 : public TObject {
private:
	Integer FIntegerValue;
	String FStringValue;
 
public:
	__property Integer IntegerValue = {
		read = FIntegerValue, write = FIntegerValue};
	__property String StringValue = {read = FStringValue, write = FStringValue};
};
 
class TMyObject2 : public TObject {
private:
	Integer FIntegerValue;
	String FStringValue;
 
public:
	__property Integer IntegerValue = {
		read = FIntegerValue, write = FIntegerValue};
	__property String StringValue = {read = FStringValue, write = FStringValue};
};
 
class TMyResultObject : public TObject {
private:
	Integer FIntegerValue;
	String FStringValue;
 
public:
	__property Integer IntegerValue = {
		read = FIntegerValue, write = FIntegerValue};
	__property String StringValue = {read = FStringValue, write = FStringValue};
};
 
int _tmain(int argc, _TCHAR* argv[]) {
	TMyObject1 *MyObject1;
	TMyObject2 *MyObject2;
	TMyResultObject *MyResultObject;
 
	TBindingExpression *BindingExpression1, *BindingExpression2;
 
	MyObject1 = new TMyObject1();
	MyObject2 = new TMyObject2();
	MyResultObject = new TMyResultObject();
 
	MyObject1->IntegerValue = 1;
	MyObject1->StringValue = "LiveBinding ";
	MyObject2->IntegerValue = 2;
	MyObject2->StringValue = "power.";
 
	try {
		try {
			OpenArray<_di_IScope>InputScopes
				(TBindings::CreateAssociationScope
				(OPENARRAY(TBindingAssociation, (Associate(MyObject1, "o1"),
				Associate(MyObject2, "o2")))));
			OpenArray<_di_IScope>OutputScopes
				(TBindings::CreateAssociationScope
				(OPENARRAY(TBindingAssociation, (Associate(MyResultObject,
				"res")))));
 
			BindingExpression1 = TBindings::CreateManagedBinding(InputScopes,
				InputScopes.GetHigh(), "o1.IntegerValue + o2.IntegerValue",
				OutputScopes, OutputScopes.GetHigh(), "res.IntegerValue", NULL);
 
			BindingExpression2 = TBindings::CreateManagedBinding(InputScopes,
				InputScopes.GetHigh(), "o1.StringValue + o2.StringValue",
				OutputScopes, OutputScopes.GetHigh(), "res.StringValue", NULL);
 
			TBindings::Notify(MyObject1, "IntegerValue");
			TBindings::Notify(MyObject1, "StringValue");
 
			printf("Result of add operation: %d\n", MyResultObject->IntegerValue);
			printf("%ls\n", MyResultObject->StringValue.c_str());
		}
		catch (Exception& e) {
			printf("%ls\n", e.ToString().c_str());
		}
	}
	__finally {
		delete MyObject1;
		delete MyObject2;
		delete MyResultObject;
	}
 
	return 0;
}

Results interpretation

The program described in this tutorial is used to bind four properties of two different objects through binding expressions. Two of these properties are of type Integer; you performed an addition using them. The other two properties are of type string; you performed a concatenation using them.

By running the program, the console output should be as follows.

Result of add operation: 3
LiveBinding power.

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