CODEWITHSUNDEEP
delphidynamicdelphi-2010procedures
Visiobibliophobia
Visiobibliophobia

Reputation: 63

Dynamic objects with an event handler - Delphi

I have two components created dynamically, a button (btnEnter) and an edit (edtID)- where the user will enter their user ID. What I want is for the program to verify whether the user has entered a valid ID when they have clicked the button.

The code I have:

1)When the objects are created

    with btnEnter do
    {edit properties such as caption, etc}
    OnClick := ValidateID;

2)The procedure is declared as follows:

    procedure ValidateID (Sender : TObject);

What I would like to do is pass the text in the edit through the procedure as a parameter, so that the procedure will be able to manipulate the text and determine whether it is valid or not.

So what I tried, but didn't work was:

    procedure ValidateID (Sender : TObject; sID : string);

    with btnEnter do
    OnClick := ValidateID(edtID.Text);

Would really appreciate if someone could help me with this. Thanks

Upvotes: 1

Views: 4629

Answers (2)

asd-tm
asd-tm

Reputation: 5238

This code works.

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)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    button: TButton;
    edit: TEdit;
    procedure ValidateID(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}


procedure TForm1.FormCreate(Sender: TObject);
begin
  edit := TEdit.Create(self);
  button := TButton.Create(self);
  button.Parent := Form1;
  edit.Parent := Form1;
  edit.Left := 1;
  edit.Top := 1;
  button.Left := 1;
  button.Top := 50;
  button.OnClick := ValidateID;
end;

procedure TForm1.ValidateID(Sender: TObject);
begin
  ShowMessage(edit.Text)
end;

end.

Upvotes: 1

Tom Brunberg
Tom Brunberg

Reputation: 21033

The TButton.OnClick event is of type TNotifyEvent which has a signature:

  TNotifyEvent = procedure(Sender: TObject) of object;

Thus, you can not assign a procedure with a different signature to TButton.OnClick.

You need to declare the ValidateID procedure as a method of the form class and then, since the TEdit is on the same form, it is in the same scope as your validation method, and you can simply access EditID.Text in your ValidateID method.

Upvotes: 2

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