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<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2>Thanks for that Todd.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2>I'll go back and check my code, but I'm never referring to
my list via an interface, and it seems to be fine so far.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2>Cheers,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=852315023-12062006><FONT face=Arial
color=#0000ff size=2>C.</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> delphi-bounces@ns3.123.co.nz
[mailto:delphi-bounces@ns3.123.co.nz] <B>On Behalf Of </B>Todd
Martin<BR><B>Sent:</B> Tuesday, 13 June 2006 11:37 a.m.<BR><B>To:</B> NZ Borland
Developers Group - Delphi List<BR><B>Subject:</B> Re: [DUG] (no
subject)<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV><FONT face=Arial size=2>Ah. I'm sorry I disagree.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Firstly, Andrew wanted to add a TAOleCoordinate to
his TAOleCoordinateList. So the Add() method expected a TAOleCoordinate
parameter, NOT a TAOleCoordinateList parameter.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Secondly, there is no need to always reference
TInterfaceList with an interface.</FONT></DIV>
<DIV><FONT face=Arial size=2>So the declaration</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>TMyClass=class(TObject)</FONT></DIV>
<DIV><FONT face=Arial size=2>private</FONT></DIV>
<DIV><FONT face=Arial size=2> FInterfaceList :
TInterfaceList;</FONT></DIV>
<DIV><FONT face=Arial size=2>end;</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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().</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Conor, </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>procedure SomeMethod()</FONT></DIV>
<DIV><FONT face=Arial size=2>var</FONT></DIV>
<DIV><FONT face=Arial size=2> LocalList : IInterfaceList; //interface
variable</FONT></DIV>
<DIV><FONT face=Arial size=2>begin</FONT></DIV>
<DIV><FONT face=Arial size=2> MyObject := TMyClass.Create();</FONT></DIV>
<DIV><FONT face=Arial size=2> LocalList :=
MyObject.FInterfaceList;</FONT></DIV>
<DIV><FONT face=Arial size=2>// LocalList.Add(AInterface);</FONT></DIV>
<DIV><FONT face=Arial size=2>....</FONT></DIV>
<DIV><FONT face=Arial size=2>end;</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>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!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Personally, to enforce encapsulation, I think
FInterface should never be accessed directly. You should add methods to your
containing object instead. Like so</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>
<DIV><FONT face=Arial size=2>TMyClass=class(TObject)</FONT></DIV>
<DIV><FONT face=Arial size=2>private</FONT></DIV>
<DIV><FONT face=Arial size=2> FInterfaceList :
TInterfaceList;</FONT></DIV>
<DIV>public</DIV>
<DIV> function Add(AInterface : IInterface) : Integer;</DIV>
<DIV> function Remove(AInterface : IInterface) : Integer;</DIV>
<DIV><FONT face=Arial size=2>end;</FONT></DIV></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Which is what Andrew is doing.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Todd.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=phil@tumonz.co.nz href="mailto:phil@tumonz.co.nz">Phil Middlemiss</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=delphi@ns3.123.co.nz
href="mailto:delphi@ns3.123.co.nz">NZ Borland Developers Group - Delphi
List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, June 13, 2006 9:42
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [DUG] (no subject)</DIV>
<DIV><BR></DIV>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.<BR><BR>eg,<BR><BR>TMyObject = class(TObject)<BR>private<BR>
FInterfaceList : IInterfaceList;<BR>public<BR> constructor
create;<BR>end;<BR><BR>constructor TMyObject.create;<BR>begin<BR>
FInterfaceList := TInterfaceList; // automatic typecast to
IInterfaceList<BR>end;<BR><BR>Conor Boyd wrote:
<BLOCKQUOTE
cite=mid8285CB7241FCFC4BB721A6F953F9B35E04A66206@nzc-ap-xch-01.ap.trimblecorp.net
type="cite">
<META content="MSHTML 6.00.2900.2873" name=GENERATOR>
<DIV dir=ltr align=left><SPAN class=117441421-12062006><FONT face=Arial
color=#0000ff size=2>Can you clarify that for me?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006><FONT face=Arial
color=#0000ff size=2>Why does it *need* to be referenced with an
IInterfaceList?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006><FONT face=Arial
color=#0000ff size=2>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?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006><FONT face=Arial
color=#0000ff size=2>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?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006><FONT face=Arial
color=#0000ff size=2>Grateful for your thoughts...</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=117441421-12062006><FONT face=Arial
color=#0000ff size=2>C.</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
</DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma><FONT size=2><B>From:</B> <A class=moz-txt-link-abbreviated
href="mailto:delphi-bounces@ns3.123.co.nz">delphi-bounces@ns3.123.co.nz</A>
[<A class=moz-txt-link-freetext
href="mailto:delphi-bounces@ns3.123.co.nz">mailto:delphi-bounces@ns3.123.co.nz</A>]
<B>On Behalf Of </B>Phil Middlemiss<BR><SPAN class=117441421-12062006><FONT
face=Arial color=#0000ff> </FONT></SPAN></FONT></FONT></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>No, it wasn't
a typo - he needs to *create* a TInterfaceList - but that list needs to be
*referenced* with an IInterfaceList. It was intentional to force Thomas to
look up how to end up with a working IInterfaceList.<BR><BR>Conor Boyd
wrote: </DIV>
<BLOCKQUOTE
cite=mid8285CB7241FCFC4BB721A6F953F9B35E04A661A3@nzc-ap-xch-01.ap.trimblecorp.net
type="cite">
<META content="MSHTML 6.00.2900.2873" name=GENERATOR>
<DIV dir=ltr align=left><SPAN class=552015620-12062006><FONT face=Arial
color=#0000ff size=2>I'm sure it was just a typo, but it should be a
TInterfaceList instead of a TList.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=552015620-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=552015620-12062006><FONT face=Arial
color=#0000ff size=2>Cheers,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=552015620-12062006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=552015620-12062006><FONT face=Arial
color=#0000ff size=2>Conor</FONT></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
</DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma><FONT size=2><B>From:</B> <A class=moz-txt-link-abbreviated
href="mailto:delphi-bounces@ns3.123.co.nz">delphi-bounces@ns3.123.co.nz</A>
[<A class=moz-txt-link-freetext
href="mailto:delphi-bounces@ns3.123.co.nz">mailto:delphi-bounces@ns3.123.co.nz</A>]
<B>On Behalf Of </B>Phil Middlemiss<BR><SPAN
class=552015620-12062006><FONT face=Arial
color=#0000ff> </FONT></SPAN></FONT></FONT></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma><FONT size=2><SPAN
class=552015620-12062006></SPAN></FONT></FONT><FONT face=Tahoma><FONT
size=2><SPAN class=552015620-12062006><FONT face=Arial
size=2>[snip]</FONT> </SPAN></FONT></FONT></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><SPAN
class=552015620-12062006></SPAN> </DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>You should
also be adding it to an IInterfaceList instead of a TList.<BR><BR>
<P><FONT face=Arial size=2>[snip]</FONT> </P></DIV></BLOCKQUOTE><PRE wrap=""><HR width="90%" SIZE=4>
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