BTW, the problem you were having below is that when you shoved the
interface into the Tlist, the reference count was not incremented. So,
at some point, the object behind the interface got freed... And bang
when you tried to get it back. You could have hacked around this by
call __AddRef and all the other reference counting code but it would be
a hack and messy. Much cleaner to use the TinterfaceList (which also
has its own interface, IInterfaceList).

Regards,
Tom

-----Original Message-----
From: delphigames@yahoogroups.com [mailto:delphigames@yahoogroups.com]
On Behalf Of Grubb, Thomas G. (GSFC-583.0)
Sent: Tuesday, February 10, 2009 10:08 AM
To: delphigames@yahoogroups.com
Subject: RE: [DelphiGames] Casting an object to an interface

Hi Ian Munro,
Use a TInterfaceList. That is a TList for interfaces.
Regards,
Tom

-----Original Message-----
From: delphigames@yahoogroups.com [mailto:delphigames@yahoogroups.com]
On Behalf Of Ian Munro
Sent: Tuesday, February 10, 2009 6:39 AM
To: delphigames@yahoogroups.com
Subject: [DelphiGames] Casting an object to an interface

Hello,



I need to store references to interfaces in a list so that when the user
selects a list item I can easily access the interface that relates to
that item. I've been casting the interface as a pointer and adding it as
the list items object. Now when I try to retrieve it I try to cast it
back and the compiler moans that you cant cast a TObject to an
interface. I tried casting it to a pointer first and then to the
interface type which the compiler likes (see code below). The problem I
have then is that when the code runs, when the following line runs it
throws an exception. My question is, Is there a better way to do what I
need to do and what is causing the problem with this code. I must say
that I'm not 100% when it comes to interfaces.



Item := IJanusDataSourceItem (pointer (ListItemObject)) ;








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