Did you know…?

Did you know that you can get and set events with the TMethod record? Let’s assume you would like to hook an OnClose event of a form:

type
  TMyHookObject = class
  strict private
    FOldOnClose: TMethod;
    procedure OnClose(ASender: TObject; var AAction: TCloseAction);
...

procedure TMyHookObject.Init(AForm: TForm);
begin
  //Save the old event
  FOldOnClose := TMethod(AForm.OnClose);
  //Set the new one
  AForm.OnClose := OnClose;
end;

procedure TMyHookObject.OnClose(ASender: TObject; var AAction: TCloseAction);
begin
  //Call the old event
  if Assigned(FOldOnClose.Data) and Assigned(FOldOnClose.Code) then
    TCloseEvent(FOldOnClose)(ASender, AAction);
  
  //Run your own code
  ...

As you can see in the example you can easily store and call events with the help of TMethod.