Solved

Form Inheritance

Posted on 1998-01-08
2
306 Views
Last Modified: 2010-04-04
I am trying to create a base form so that I can have a standard base for all of the forms in a project. The code for the BaseForm is as follows:-

unit main;

interface

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

type
  TBaseForm = class(TForm)
    btnClose: TButton;
    procedure tobtnExitClick(Sender: TObject);
    procedure btnCloseClick(Sender: TObject);
  private

  published
    procedure ExitItemClickAction; virtual;

  public
    constructor Create(AOwner: TComponent); override;
  end;

var
  BaseForm: TBaseForm;

implementation

{$R *.DFM}

constructor TBaseForm.Create(AOwner: TComponent);
begin
    inherited Create(AOwner);
    RegisterClasses([TButton]);
    if ClassName <> 'TBaseForm' then
    ReadComponentRes('TBaseForm',Self);
end;


procedure TBaseForm.tobtnExitClick(Sender: TObject);
begin
    ExitItemClickAction;
end;

procedure TBaseForm.ExitItemClickAction;
begin
    Close;
end;

procedure TBaseForm.btnCloseClick(Sender: TObject);
begin
    ExitItemClickAction;
end;

end.

This compiles and runs properly. However when I create a derived form and run that I get an error that tells me that the btnClose already exists and so the form will not compile. This is the code for the derived form:-

unit derivedfrm;

interface

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

type
  TDerivedForm = class(TBaseForm)
    Memo1: TMemo;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  DerivedForm: TDerivedForm;

implementation

{$R *.DFM}


end.


What am I doing wrong?

Thanks in anticipation.

Alan Ward
0
Comment
Question by:alanward
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 3

Expert Comment

by:Matvey
ID: 1355946
Sorry, but I don't understand your Create method.
Registering components - what for? You must understand that all the instances of your form are created by this method, and register the same thing - it might be the problem, but I'm not sure.

The error itself occures in the last line of this method:
          ReadComponentRes('TBaseForm',Self)

What for is this?

What for do you register a button?

Matvey
0
 
LVL 1

Accepted Solution

by:
miv earned 100 total points
ID: 1355947
Move your private declaration up in front of the vars and procedures.
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Delphi 2 77
Convert a string into a TDateTime 5 72
tvirtualstringtree freeze when load too manny images 10 80
Can Live bindings change TGrid Cell Colour ? 1 31
The uses clause is one of those things that just tends to grow and grow. Most of the time this is in the main form, as it's from this form that all others are called. If you have a big application (including many forms), the uses clause in the in…
This article explains how to create forms/units independent of other forms/units object names in a delphi project. Have you ever created a form for user input in a Delphi project and then had the need to have that same form in a other Delphi proj…
Email security requires an ever evolving service that stays up to date with counter-evolving threats. The Email Laundry perform Research and Development to ensure their email security service evolves faster than cyber criminals. We apply our Threat…
Attackers love to prey on accounts that have privileges. Reducing privileged accounts and protecting privileged accounts therefore is paramount. Users, groups, and service accounts need to be protected to help protect the entire Active Directory …

749 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question