How to create Delphi component inherited from few other components? - delphi

Question

Tutorials that I found about how to create delphi components were nice, but they only used one of existing components as object to inherit actions from. Something like this
unit CountBtn;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, ExtCtrls;
type
TCountBtn = class(TButton)
private
FCount: integer;
protected
procedure Click;override;
public
procedure ShowCount;
published
property Count:integer read FCount write FCount;
constructor Create(aowner:Tcomponent); override;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Mihan Components', [TCountBtn]);
end;
constructor TCountBtn.Create(aowner:Tcomponent);
begin
inherited create(Aowner);
end;
procedure Tcountbtn.Click;
begin
inherited click;
FCount:=FCount+1;
end;
procedure TCountBtn.ShowCount;
begin
Showmessage('On button '+ caption+' you clicked: '+inttostr(FCount)+' times');
end;
end.
But what should I do if I need component which use few elements? Lets say, I got Button and Edit field. And on button click there in edit field should appers text the same as on button. I start to make it like this, but seems like it's not gonna work as I want:
unit TestComp;
interface
uses
System.SysUtils, System.Classes, Vcl.Controls, Vcl.StdCtrls, Vcl.ExtCtrls;
type
TUiCompU = class(TCustomControl)
private
{ Private declarations }
FButton: TButton;
FEdit: TEdit;
protected
{ Protected declarations }
procedure Paint; override;
//wrong!
procedure FButton.Click;override
public
{ Public declarations }
constructor Create(AOwner: TComponent); override;
published
{ Published declarations }
//wrong!
property ButtonText: String read FButton.Caption write FButton.Caption;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Ui', [TUiCompU]);
end;
{ TUiCompU }
constructor TUiCompU.Create(AOwner: TComponent);
begin
inherited;
Width := 200;
Height := 50;
FButton := TButton.Create(Self);
FButton.SetSubComponent(True);
FButton.Parent := Self;
FButton.Top := 8;
FButton.Left := 50;
FButton.Width := 35;
FButton.Name := 'Button';
FEdit := TEdit.Create(Self);
FEdit.SetSubComponent(True);
FEdit.Parent := Self;
FEdit.Top := 8;
FEdit.Left := 84;
FEdit.Width := 121;
FEdit.Name := 'Edit';
end;
procedure TUiCompU.Paint;
begin
Canvas.Rectangle(ClientRect);
end;
end.
How should I add here Click procedure, which is realte to click on the button? And is there are good tutorial about how to made good components using others? (I need to create something like slideshow component btw).
Thank you, and sorry for my english.

Answer 1

You can write methods for the subcomponent events, but it has one big weakness; if you publish those subcomponents, there is a risk that someone will steal you this binding by writing own method:
type
TUiCompU = class(TCustomControl)
private
FEdit: TEdit;
FButton: TButton;
procedure ButtonClick(Sender: TObject);
procedure EditKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
public
constructor Create(AOwner: TComponent); override;
end;
implementation
constructor TUiCompU.Create(AOwner: TComponent);
begin
inherited;
FButton := TButton.Create(Self);
...
FButton.OnClick := ButtonClick;
FEdit := TEdit.Create(Self);
...
FEdit.OnKeyDown := EditKeyDown;
end;
procedure TUiCompU.ButtonClick(Sender: TObject);
begin
// do whatever you want here
end;
procedure TUiCompU.EditKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
// do whatever you want here
end;