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Attach a function to an event handler

boardtc
boardtc asked
on
Medium Priority
192 Views
Last Modified: 2010-04-04
How can I attach a function which is declared in another unit to an event handler, say OnDoubleClick. It seems what you attach in code must be declared in the class (published section).

Thanks,

Tom.
Comment
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Commented:
I think this is what you want,

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    procedure WriteHallo;
  end;

var
  Form1: TForm1;

implementation

uses Unit2;

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
 Form2.ShowModal;
end;

procedure TForm1.WriteHallo;
begin
 label1.Caption := 'Hello, Tom is this what you want?';
end;

end.

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls, StdCtrls;

type
  TForm2 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

uses Unit1; { <-------- THIS NEEDS TO BE HERE }

{$R *.DFM}

procedure TForm2.Button1Click(Sender: TObject);
begin
 {Add Unit1 to uses list}
 Form1.WriteHallo;
end;

end.

Author

Commented:
?? I don't follow what you are trying.

What i want to do in thre form create is:

TPanel.OnDblClick := MyFunction;

where my function is a function declared in another unit.

Thanks,

Tom.

Commented:
Ah, now I get it.
But my solution works too. If you push the button in Form2 then in Form1 the text in caption1 will be changed (thanks to procedure WriteHallo) -> look at form1 after pushing button on form2.

If you put in your TPanel.OnDblClick the following code :
FormName.FunctionName then this will be activated when you double click on tpanel. This is the easiest way to do it.

Author

Commented:
Ok, the later makes sense, I'll do it that way, I should have thought of that. Put an answer in so I can grade you. Tom.
Commented:
Ok, here is the example, same as the first one but now procedure will be called after you doubleclick the panel on form2.

- FORM1 ------------------------------------------------------

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    procedure WriteHello;
  end;

var
  Form1: TForm1;

implementation

uses Unit2;

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
 Form2.ShowModal;
end;

procedure TForm1.WriteHello;
begin
 label1.Color   := clRed;
 label1.Caption := 'Hello, Tom is this what you want?';
end;

end.

- FORM2 -------------------------------------------------------

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls, StdCtrls;

type
  TForm2 = class(TForm)
    Panel1: TPanel;
    procedure Panel1DblClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

uses Unit1;

{$R *.DFM}

procedure TForm2.Panel1DblClick(Sender: TObject);
begin
 {Add Unit1 to uses list}
 Form1.WriteHello;
end;

end.

Have fun,
c.u. ZifNab;

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Author

Commented:
calling the function in a handler was the way to go rather than trying to attach to the handler.
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