How to free control inside its event handler?

by

The solution is to post a queued message to the control, which it responds to by destroying itself. Ny convention we use CM_RELEASE which is the private message used by TForm in its implementation of the Release method that performs an analogous task. 

interface

type
  TAmountEdit = class (TEdit)
    ...
    procedure KeyUp(var Key: Word; Shift :TShiftState); override;
    procedure HandleRelease(var Msg: TMessage); message CM_RELEASE;
    ...
  end;

implementation

procedure TAmountEdit.KeyUp(var Key: Word; Shift :TShiftState);
begin
  inherited;
  if Text="" then
    PostMessage(Handle, CM_RELEASE, 0, 0);
end;

procedure TAmountEdit.HandleRelease(var Msg: TMessage);
begin
  Free;
end;

The control is destroyed when the application next pumps its message queue.

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