Show: Delphi C++
Display Preferences

Code Generated When You Import Type Library Information

From RAD Studio XE2
Jump to: navigation, search

Go Up to Creating COM clients Index

Once you import a type library, you can view the generated TypeLibName_TLB unit. At the top, you will find the following:

1. First, constant declarations giving symbolic names to the GUIDS of the type library and its interfaces and CoClasses. The names for these constants are generated as follows:

  • The GUID for the type library has the form LBID_TypeLibName, where TypeLibName is the name of the type library.
  • The GUID for an interface has the form IID_InterfaceName, where InterfaceName is the name of the interface.
  • The GUID for a dispinterface has the form DIID_InterfaceName, where InterfaceName is the name of the dispinterface.
  • The GUID for a CoClass has the form CLASS_ClassName, where ClassName is the name of the CoClass.
  • The compiler directive VARPROPSETTER will be on. This allows the use of the keyword var in the parameter list of property setter methods. This disables a compiler optimization that would cause parameters to be passed by value instead of by reference. The VARPROPSETTER directive must be on, when creating TLB units for components written in a language other than Delphi.

2. Second, declarations for the CoClasses in the type library. These map each CoClass to its default interface.

3. Third, declarations for the interfaces and dispinterfaces in the type library.

4. Fourth, declarations for a creator class for each CoClass whose default interface supports VTable binding. The creator class has two class methods, Create and CreateRemote, which can be used to instantiate the CoClass locally (Create) or remotely (CreateRemote). These methods return the default interface for the CoClass.

These declarations provide you with what you need to create instances of the CoClass and access its interface. All you need to do is add the generated TypeLibName_TLB.pas file to the uses clause of the unit where you want to bind to a CoClass and call its interfaces.

Note: This portion of the TypeLibName_TLB unit is also generated when you use the Type Library editor or the command-line utility TLIBIMP.

If you want to use an ActiveX control, you also need the generated VCL wrapper in addition to the declarations described above. The VCL wrapper handles window management issues for the control. You may also have generated a VCL wrapper for other CoClasses in the Import Type Library dialog. These VCL wrappers simplify the task of creating server objects and calling their methods. They are especially recommended if you want your client application to respond to events.

The declarations for generated VCL wrappers appear at the bottom of the interface section. Component wrappers for ActiveX controls are descendants of Vcl.OleCtrls.TOleControl. Component wrappers for Automation objects descend from Vcl.OleServer.TOleServer. The generated component wrapper adds the properties, events, and methods exposed by the CoClass's interface. You can use this component like any other VCL component.

Warning: You should not edit the generated TypeLibName_TLB unit. It is regenerated each time the type library is refreshed, so any changes will be overwritten.
Note: For the most up-to-date information about the generated code, refer to the comments in the automatically generated TypeLibName_TLB unit.

See Also

Personal tools
Previous Versions
In other languages