Classes.GetClass Function

Returns a registered persistent class given its name.

Pascal

function GetClass(const AClassName: string): TPersistentClass;

C++

TPersistentClass GetClass(const AnsiString AClassName);

File

Classes

Description

Call GetClass to obtain a class from a class name. This class can be used as a parameter to routines that require a class.

The Class must be registered before GetClass can find it. Form classes and component classes that are referenced in a form declaration (instance variables) are automatically registered when the form is loaded. Other classes can be registered by calling RegisterClass or RegisterClasses.

Note: To obtain an unregistered class from a class name in C++, use the __classid routine.

C++ Examples:

Copy Code

/*
The following example allows users to type the name of a
graphics class into an edit control and when a button is
pressed, the name of the default extension for that class is
displayed in another edit control.  In the form’s OnCreate
event handler (or a similar place) you must register the
graphics classes so that GetClass can find them.
*/
TMetaClass *MetaClass;

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  TClassFinder *myClassFinder = new TClassFinder(MetaClass, False);
  TGraphicClass mygraphclass = (TGraphicClass) (myClassFinder->GetClass(Edit2->Text));
//  TGraphicClass mygraphclass = (TGraphicClass) GetClass(Edit2->Text);
  Edit1->Text = GraphicExtension(mygraphclass);
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  MetaClass = __classid(TIcon); // ico
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(Graphics::TBitmap); // bmp
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(TMetafile); // emf
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(TShape);  // nographic extension
  RegisterClasses(&MetaClass, 0);
  MetaClass = __classid(TImage); // nographic extension
  RegisterClasses(&MetaClass, 0);
}

Delphi Examples:

Copy Code

{
The following example allows users to type the name of a
graphics class into an edit control and when a button is
pressed, the name of the default extension for that class is
displayed in another edit control.  In the form’s OnCreate
event handler (or a similar place) you must register the
graphics classes so that GetClass can find them.
}

uses ExtCtrls;

procedure TForm1.Button1Click(Sender: TObject);
var
  myClassFinder: TClassFinder;
  mygraphclass: TGraphicClass;
begin
  { make sure the classes are registered so that GetClass will work -- }
  { Usually, this goes in the initialization section where it is only executed once }
  RegisterClasses([TIcon, TBitmap, TButton, TShape, TImage, TMetafile]);
  try
    myClassFinder := TClassFinder.Create(TIcon, False);
    mygraphclass := TGraphicClass(myClassFinder.GetClass(Edit2.Text));
//    mygraphclass := TGraphicClass(GetClass(Edit2.Text));  // works as well
    Edit1.Text := GraphicExtension(mygraphclass);
  except
    on EAccessViolation do
      MessageDlg('Invalid class name.', mtError, [mbOK], 0)
  end;
end;