Ah. I'm sorry I disagree.
Firstly, Andrew wanted to add a
TAOleCoordinate to his TAOleCoordinateList. So the Add() method
expected a TAOleCoordinate parameter, NOT a TAOleCoordinateList
parameter.
Secondly, there is no need to always
reference TInterfaceList with an interface.
So the declaration
TMyClass=class(TObject)
private
FInterfaceList : TInterfaceList;
end;
is fine, provided you NEVER extract
an interface reference to the list object. The reference count in
FInterfaceList starts at zero, when it is created, and remains at zero,
and is destroyed with FInterfaceList.Free().
Conor,
the reason you need to use _AddRef
on your TInterfaceList, is that somewhere in your code you are refering
to the internal list with something like this
procedure SomeMethod()
var
LocalList : IInterfaceList;
//interface variable
begin
MyObject := TMyClass.Create();
LocalList :=
MyObject.FInterfaceList;
// LocalList.Add(AInterface);
....
end;
this extracts an interface reference
to FInterfaceList and increases the reference count to 1. As soon as
LocalList goes out of scope, ie at the end of SomeMethod(), the
reference count drops back to zero and FInterfaceList is destroyed!
Personally, to enforce
encapsulation, I think FInterface should never be accessed directly.
You should add methods to your containing object instead. Like so
TMyClass=class(TObject)
private
FInterfaceList : TInterfaceList;
public
function Add(AInterface : IInterface) : Integer;
function Remove(AInterface : IInterface) : Integer;
end;
Which is what Andrew is doing.
Todd.
----- Original Message -----
Sent:
Tuesday, June 13, 2006 9:42 AM
Subject:
Re: [DUG] (no subject)
TInterfaceList is descended from TInterfacedObject, so it needs to be
referenced with an interface to keeps it's reference count above 0 -
else it will be destroyed along with all the objects it contains.
eg,
TMyObject = class(TObject)
private
FInterfaceList : IInterfaceList;
public
constructor create;
end;
constructor TMyObject.create;
begin
FInterfaceList := TInterfaceList; // automatic typecast to
IInterfaceList
end;
Conor Boyd wrote:
Can you clarify that for me?
Why does it *need* to be
referenced with an IInterfaceList?
I've just started using a
TInterfaceList to hold references to interfaces, but I don't see why I
have to use interfaces WRT the list itself?
Having said that, I have an
issue where I have to explicitly call _AddRef on the interface I'm
adding to my interfacelist to keep it alive. Could these two things be
related?
Grateful for your thoughts...
C.
I'm sure it was just a typo, but
it should be a TInterfaceList instead of a TList.
Cheers,
Conor
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