Pointers to member functions.

Posted on 2001-09-01
Last Modified: 2011-09-20
Well, here goes:
I have a certain component with member functions that should be used as callbacks for a DLL I am wrapping. Now the problem is: when the functions are global, and not members of a class, I can get a pointer to them just by writing @Func.

But how do I get a pointer to a member function?
Question by:fulg0re
  • 2
LVL 14

Accepted Solution

DragonSlayer earned 300 total points
ID: 6449518
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);

    procedure Hello_World(Sender: TObject); // Your routines (that you'll run by name) must be here
    { Private declarations }
    procedure ExecuteRoutine(Instance: TObject; Name: string);
    { Public declarations }

  Form1: TForm1;

   TExecute = procedure (Sender: TObject) of object;

// The most important routine
procedure TForm1.ExecuteRoutine(Instance: TObject; Name: string; Param: TObject);
  Routine: TMethod;
  Execute: TExecute;
  Routine.Data := Pointer(Instance);
  Routine.Code := Instance.MethodAddress(Name); // Returns the address of a published method.
  MethodAddress is used internally by the streaming system.
  When an event property is read from a stream, MethodAddress converts a method name,
  specified by Name, to a pointer containing the method address.
  There should be no need to call MethodAddress directly.

  If Name does not specify a published method for the object, MethodAddress returns nil.
  if Routine.Code = nil then Exit;
  Execute := TExecute(Routine);

procedure TForm1.Button1Click(Sender: TObject);
  ExecuteRoutine(Form1, 'Hello_World', nil);

procedure TForm1.Hello_World(Sender: TObject);
  ShowMessage('This is a test');
LVL 20

Expert Comment

ID: 6450010
Beware of fulg0re, he bought my components with a fraud credit card. I'm serious.
LVL 14

Expert Comment

ID: 6450031
oh dear...

if it's true, fulg0re, then you are being a BAD boy...

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