callback
From Free Pascal wiki
Jump to navigationJump to search
Callback functions are in widespread usage in Lazarus; in fact any Event is made available using 'callback'.
type TForm = class(TForm) btn: TButton; procedure btnClick(Sender: TObject); end; ... procedure TForm.btnClick(Sender: TObject); begin // dosomething end;
The btnClick method is a callback from within the TButton implementation.
Apart from their use in the userinterface of a form, callbacks are used in many libraries that were linked.