Question

I have a shape, when i click OnMouseDown in Object inspecter / Events tab. I would like for it to do the procedure “SelectMessage” But its not showing up as an option. Also if i manually type in “SelectMessage” I get error Property and method Selectmessage are not compatible.

Selectmessage

procedure TFZone1Mod7.Selectmessage(sender: TObject);
var
  ShapeOrderNo: Integer;
begin
  if TryStrToInt(copy(TShape(Sender).Name,6,MaxInt),ShapeOrderNo) then
    begin
      LookUpMessage(ShapeOrderNo);
    end;
end;

If i do

procedure TFZone1Mod7.Shape1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
   selectmessage(sender);
end;

then it will work. but easier to select from events if i can.
thanks

Answer 1

The event handler for an OnMouseEvent must have a signature of this form:

procedure (Sender: TObject; Button: TMouseButton; 
    Shift: TShiftState; X, Y: Integer) of object;

The component is going to call your event handler passing all those parameters, and your event handler must be of the expected form.

You have no control over this. The component has a pre-determined, hard-coded form for its event handlers. You simply have to fit in. Your current solution is the correct one.

Having said that, SelectMessage can only work when it is passed a TShape. So declare the function that way:

procedure TFZone1Mod7.SelectMessage(Shape: TShape);
var
  ShapeOrderNo: Integer;
begin
  if TryStrToInt(copy(Shape.Name,6,MaxInt), ShapeOrderNo) then
    LookUpMessage(ShapeOrderNo);
end;

And call it like this:

procedure TFZone1Mod7.Shape1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  SelectMessage(Sender as TShape);
end;