Delphi: Incompatible type: 'method pointer and regular procedure' - explained

When you are creating components at run time, and want to assign a procedure to an event handler of a component, like in the following code:
procedure ButtonClick(Sender:TObject) ;
begin
//whatever
end;

procedure SomeProcedure...
var aButton:TButton;
begin
   aButton := TButton.Create(nil) ;
   aButton.OnClick = ButtonClick
...
end;

You will get the next error:
Incompatible type: 'method pointer and regular procedure'.

The problem is that a method pointer (OnClick) needs to be a procedure of an object (like TForm), not a regular procedure.

One way around is to create an object to define the procedure. You can start by creating a dummy class...

interface

type
   TEventHandlers = class // create a dummy class
       procedure ButtonClick(Sender: TObject) ;
   end;

...

var EvHandler:TEventHandlers;

implementation

procedure TEventHandlers.ButtonClick(Sender: TObject) ;
begin
   // your code here
end;

...
procedure SomeProcedure...
var aButton:TButton;
begin
   aButton := TButton.Create(nil) ;
   aButton.OnClick = ButtonClick;
...
end;

This compiles!
}

~~~~~~~~~~~~~~~~~~~~~~~~~

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