RE: [DUG]: [Q] Component Questions

[Myles Penlington]

Easy, use abstraction ..

Do this instead .. (However if you cannot change your base class you are basically stuffed ... ).

 

eg  

 TMyBaseComponent = class(TComponent)
private
   FMyProp : string;
   FOnMyEvent : TNotifyEvent;

protected

  procedure SetMyProp( const Value: String ); virtual;

  procedure DoMyEvent; virtual;
published
   property MyProp : string read FMyProp write SetMyProp;
   property OnMyEvent : TNotifyEvent read FOnMyEvent write FOnMyEvent;
end;

TMyDescendantComponent = class(TMyBaseComponent)

protected

  procedure SetMyProp( const Value: String ); override;

  procedure DoMyEvent; override;
end;

 

 

Then in

procedure DoMyEvent;

begin

  if Assigned( FOnMyEvent) then FOnMyEvent( Self );

end;

 

Depending on how things are decalred/ used, you could also hide the base versions of MyProp/MyEvent by having in the descendant your own versions, but for anything that calls the base class directly you are stuffed.

 

Myles.

-----Original Message-----
From: Donovan J. Edye [mailto:[EMAIL PROTECTED]]
Sent: Friday, 7 September 2001 11:23 a.m.
To: Multiple recipients of list delphi
Subject: [DUG]: [Q] Component Questions

G'Day All,

If I have something like:

TMyBaseComponent = class(TComponent)
private
   FMyProp : string;
   FOnMyEvent : TNotifyEvent;
published
   property MyProp : string read FMyProp write FMyProp;
   property OnMyEvent : TNotifyEvent read FOnMyEvent write FOnMyEvent;
end;

TMyDescendantComponent = class(TMyBaseComponent)


How do you elegantly in the descendant:

1. Determine when MyProp is changed so that TMyDescendantComponent can take some specialised action
2. Determine when OnMyEvent is fired so that TMyDescendantComponent can take some specialised action

TIA

-- Donovan
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Donovan J. Edye [www.edye.wattle.id.au]
Namadgi Systems [www.namsys.com.au]
Voice: +61 2 6285-3460
Fax: +61 2 6285-3459
TVisualBasic = Class(None);
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