Question

i have a method:

procedure Frob(Sender: TObject);

that i want to call when i click a menu item.

The method comes to me though an interface:

animal: IAnimal;

IAnimal = interface
   procedure Frob(Sender: TObject);
end;

The question revolves around what to assign to the OnClick event handler of a menu item (i.e. control):

var
   animal: IAnimal;
   ...
begin
   ...
   menuItem := TMenuItem.Create(FileMenu)
   menuItem.Caption := 'Click me!';
   menuItem.OnClick :=  <-------- what to do
   ...
end;

The obvious choice, my first attempt, and the wrong answer is:

   menuItem.OnClick := animal.Frob;

So how can i call a method when user clicks a control?

See also

• Why doesn’t it work?

Answer 1

Have whatever object you’re in hold the animal in a private field, then set up a method that calls it. Like so:

procedure TMyClass.AnimalFrob(Sender: TObject);
begin
   FAnimal.Frob(sender);
end;

Then the solution becomes easy:

menuItem.OnClick := self.AnimalFrob;