Hey Giovanni, RTTI info relies on you subclassing from Tpersistent. This is how Tfont etc all work also.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:owner-delphi@;delphi.org.nz] On Behalf Of Moretti, Giovanni Sent: Friday, 25 October 2002 4:15 p.m. To: Multiple recipients of list delphi Subject: RE: [DUG]: Polymorphic assignment to Color - THANKS + New Info Hi Thanks to you all for your help and the tutorial on interfaces which was very handy as I'm still wrapping my mind around them (apart from this problem). I decided to use Kyley's RTTI interrogation technique - I understand what it's doing whereas my OO development is still digesting interfaces. In due course I may go the interface way, but for the moment, the RTTI method will suffice. I decided to check the functions worked as I expected by creating my own object (rather than using Form/Panel, Font background ...) I defined a minimal object with get/set properties and tried to use it (see skeletal code below). Compiled fine but gave a "Doesn't have a Colour Property" message, which means that IsPublishedProp is returning nil. After wandering around the help system on RTTI I went home and the answer (well a solution anyway) came while I was driving. I was pondering on why the system-defined objects were fine and mine wasn't. Answer - they're all derived from TComponent. Even though the property is public and published, for "IsPublishedProp()" to work, the class (apparently) has to be a descendent of TComponent, TObject won't work. So now I have a method I can use for both VCL objects and those I create. I greatly appreciate your help Thank you all Giovanni CompSci - Massey Uni ========================================================== // TMyColourSetTester = class(TObject) <= FAILS AT RUNTIME TMyColourSetTester = class(TComponent) <= WORKS FINE private MyColour : TColor; function GetCol : TColor; procedure SetCol (value : TColor); public constructor create; // just calls inherited create published property color : TColor read GetCol write SetCol; end; procedure SetObjectColour (name : string; AObject : TObject; newColour : TColor); var result : boolean; propinfo : PPropInfo; classTypeInfo : PTypeInfo; begin result := IsPublishedProp(AObject,'color'); If result then SetOrdProp(AObject,'Color',newColour) else showmessage(name+' doesn''t have a Color property'); end; var Coltester : TMyColourSetTester; ColTester:= TMyColourSetTester.create; ColTester.color:= clYellow; // Make sure it goes setObjectColour('ColTester', ColTester, clAqua); ========================================================== ------------------------------------------------------------------------ --- New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] Website: http://www.delphi.org.nz To UnSub, send email to: [EMAIL PROTECTED] with body of "unsubscribe delphi" Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ --------------------------------------------------------------------------- New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] Website: http://www.delphi.org.nz To UnSub, send email to: [EMAIL PROTECTED] with body of "unsubscribe delphi" Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/
