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Component development in general

Posted on 2004-10-06
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Last Modified: 2013-11-23
This question is not about how to implement a TComponent descendant. I want to know more about the, err... philosophie of component development. The PME stuff (properties, methods, events), decoupling and so on. Any help or links apprechiated.
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Question by:__alex
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by:geobul
geobul earned 50 total points
ID: 12235479
Hi,

There is a help book in my D5 installation named 'Creating Custom Components'. Open it from Programs-Delphi-Help-'Creating Custom Components'.

Regards, Geo
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by:pritaeas
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ID: 12235655
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Expert Comment

by:Ivanov_G
ID: 12236531
from Delphi:
Component / New Component
1) Ancestor type   : TComponent
2) Class Name : TMyNewComponent
the rest stays default. If you want, you can put your Pallete Page something like your name.
Press OK after that.

Delphi generate some code for your. I will put some basic properties and paste the example... In published section are the properties, you seen in object inspector

unit MyNewComponent;

interface

uses
  SysUtils, Classes, Controls, Messages;

type
  TMyNewComponent = class(TComponent)
  private
    // variable for event
    OnLButton   : TMouseEvent;
    // set procedure
    procedure SetLButton (const Value : TMouseEvent);
  protected
    procedure OnLeftButton (var Msg : TMessage); message WM_LBUTTONDOWN;
  public

  published
    // this property is already know, no need to declare
    property Name;
    // declare new event
    property OnLeftMouseButton : TMouseEvent read OnLButton write SetLButton;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Samples', [TMyNewComponent]);
end;

{ TMyNewComponent }

procedure TMyNewComponent.OnLeftButton(var Msg: TMessage);
begin
  // left mouse button is clicked
  if Assigned(OnLButton) then
    OnLButton(Self, mbLeft, [], 0, 0);
end;

procedure TMyNewComponent.SetLButton(const Value: TMouseEvent);
begin
  OnLButton := Value;
end;

end.
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Expert Comment

by:ginsonic
ID: 12237575
The book that come with Delphi CD is a good start to understand the vcl development.
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by:robert_marquardt
robert_marquardt earned 50 total points
ID: 12237737
Have a look at the TLabel implementation. It is a good example on decoupling.
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BdLm earned 50 total points
ID: 12237956
components are an excellent way to reduce "double" coding, they help to keep the volume of your code small.
Its a very good way to ensure software quality.
before you write a program, think about the best way to define a object model for your data- and group
their functions and algorithms with components.
such programs will be easy to maintain and have the best options to enhance instead of re-writing from the scratch.
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by:BlackTigerX
ID: 12244144
components are very tied with OOP programming, here's all the concepts, etc of OOP

- Classes
- Design Patterns
- Owner and Parent
- Delphi OOP for beginners
- Run-Time Type Information (RTTI) In Delphi

among other things that you will find browsing through those links

http://delphi.about.com/od/oopindelphi/

and creating Delphi Components full tutorial:
http://delphi.about.com/library/bluc/text/uc061102a.htm
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Author Comment

by:__alex
ID: 12246155
Thanks for the input!
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