Mega Code Archive
Methodpointer
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Subject: Re: Pointer to a object method?
Jeff Jensen wrote:
>
> Hi
>
> I need to return a pointer to a function inside an Object, how
> can I do this?
>
> I tried using @TMyObject.MyFunction - the compiler didn't
> complain over this.
There's no reason it should complain; but then, how do you use an
untyped pointer like that to call the method?
I'd recommend using a variable of the type of the method.
Here's a quick project that demonstrates how this can be done:
-------------------->8 cut here 8<--------------------
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, Buttons, ExtCtrls;
type
TStrMethodType = procedure( S: string ) of object ;
TForm1 = class(TForm)
BitBtn1: TBitBtn;
BitBtn2: TBitBtn;
BitBtn3: TBitBtn;
procedure BitBtn1Click(Sender: TObject);
procedure BitBtn2Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure BitBtn3Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure TestMethod( S: string ) ;
end;
var
Form1: TForm1;
MethodPointer: TNotifyEvent;
MethodPointer2: TStrMethodType ;
implementation
{$R *.DFM}
procedure TForm1.TestMethod( S: string ) ;
begin
ShowMessage( S ) ;
end ;
procedure TForm1.FormCreate(Sender: TObject);
begin
MethodPointer := BitBtn1Click ;
MethodPointer2 := TestMethod ;
end;
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
ShowMessage( 'BitBtn1Click' ) ;
end;
procedure TForm1.BitBtn2Click(Sender: TObject);
begin
MethodPointer( Sender ) ;
end;
procedure TForm1.BitBtn3Click(Sender: TObject);
begin
TestMethod( 'Calling TestMethod directly' ) ;
MethodPointer2( 'Calling TestMethod via Method Pointer' ) ;
end;
end.
-------------------->8 cut here 8<--------------------
HTH
Stephen Posey
slposey@concentric.net
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