Incompatible types: 'TCloseEvent' and 'Procedure'

Question

Here is my code :

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure Button1Click(Sender: TObject);
  private
    { Déclarations privées }
  public
    { Déclarations publiques }
  end;

  TForm2 = class(TForm)
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Déclarations privées }
  public
    { Déclarations publiques }
    // I try to put it here but the same problem
    //procedure FormClose(Sender: TObject; var Action: TCloseAction);
  end;
var
  Form1: TForm1;
  Form2: TForm2;
implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
Form2 := TForm2.CreateNew(Application);
Form2.Parent := Self;
Form2.OnClose := TForm2.FormClose;
Form2.Show;
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  ShowMessage('Form1Close');
end;

procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin
   ShowMessage('Form2Close');
end;
end.

When I try to assign FormClose to OnClose event of the Form2 , I got the following error Msg:

[Dcc32 Error] Unit1.pas (40): E2010 Incompatible types: 'TCloseEvent' and 'Procedure'

When I change it to :

Form2.OnClose := FormClose;

It works fine,but that is like Self.FormClose , not the TForm2.FormClose procedure.

How can I assign TForm2.FormClose to Form2.Onclose?

I didn't realize it was even possible to have two forms in the same unit... Obviously, two classes are normal. But do both of these forms also share the same DFM? How would that even work? — Jerry Dodge, Jul 26 '17 at 19:23
@Jerry the dfm defines only one form's properties. The other one has no dfm, hence the use of CreateNew. — David Heffernan, Jul 26 '17 at 21:14

score 3 · Accepted Answer · answered Jul 26 '17 at 19:14

Change TForm2.FormClose to Form2.FormClose:

Form2.OnClose := Form2.FormClose;

However, since you want the OnClose event to be associated with a handler that belongs to the same object you just created, it would be better to just move TForm2 to a separate unit with its own design-time DFM, and then you can assign the TForm2.OnClose event at design-time and let the DFM hook it up for you when TForm2.Create() is called at runtime:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure Button1Click(Sender: TObject);
  private
    { Déclarations privées }
  public
    { Déclarations publiques }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses
  Unit2;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Form2 := TForm2.Create(Application);
  Form2.Parent := Self;
  Form2.Show;
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  ShowMessage('Form1Close');
end;

end.

unit Unit2;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm2 = class(TForm)
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Déclarations privées }
  public
    { Déclarations publiques }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
begin
   ShowMessage('Form2Close');
end;

end.

Thank you man , Sometimes people lose their focus completely :) — Ilyes, Jul 26 '17 at 19:18

Incompatible types: 'TCloseEvent' and 'Procedure'

1 Answers1