<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 11 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]--><o:SmartTagType
namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="Street"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="address"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="country-region"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="place"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="PersonName"/>
<!--[if !mso]>
<style>
st1\:*{behavior:url(#default#ieooui) }
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:blue;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:Arial;
color:navy;}
@page Section1
{size:21.0cm 842.0pt;
margin:72.0pt 89.85pt 72.0pt 89.85pt;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=blue>
<div class=Section1>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Carefully ;-).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>You need to make sure all interface
references are out of scope before you free the object. The best way I found
was to implement an interface method which returns the object as a TWinControl (in
my case – TObject would probably work too). Then do the following code:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> LWinControl
:= LInterface.WinControl;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> LInterface:=
nil;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> // Now that
the interface reference has been released we can do free. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
LWinControl.Free;<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Add try’s as necessary for the level
of memory protection/error handling that you require.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>David.</span></font><font color=navy><span
style='color:navy'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'> </span></font><o:p></o:p></p>
</div>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
delphi-bounces@ns3.123.co.nz [mailto:delphi-bounces@ns3.123.co.nz] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Stacey Verner<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, 29 September 2005
3:06 p.m.<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">NZ
Borland Developers Group - <st1:place w:st="on">Delphi</st1:place> List</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> [DUG] How do you free an
Object Instance when you have an InterfaceReference?</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>If you have an object the implements and interface, and you
have a reference<br>
to the interface, how do you free the object using the reference to the
interface?</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I have the following (simplified) interface and classes.</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>interface</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>type</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'> IMyMenuItem = interface<br>
function AddMenuItem(PCaption: String; POnClick:
TNotifyEvent): IMyMenuItem;<br>
procedure MyFree;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'> TMyMenuItem = class(TMenuItem, IMyMenuItem)<br>
public<br>
function AddMenuItem(PCaption: String; POnClick:
TNotifyEvent): IMyMenuItem;<br>
procedure MyFree;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'> TMyTBMenuItem = class(TTBItem, IMyMenuItem)<br>
public<br>
function AddMenuItem(PCaption: String; POnClick:
TNotifyEvent): IMyMenuItem;<br>
procedure MyFree;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>implementation;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>function TMyMenuItem.AddMenuItem(PCaption: String;
POnClick: TNotifyEvent): IMyMenuItem;<br>
var<br>
LMenuItem: TMyMenuItem;<br>
begin<br>
LMenuItem := TMyMenuItem.Create(PParent.Owner);<br>
LMenuItem.Caption := PCaption;<br>
LMenuItem.OnClick := POnClick;<br>
Result := LMenuItem;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>procedure TMyMenuItem.MyFree;<br>
begin<br>
Free;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>function TMyTBMenuItem.AddMenuItem(PCaption: String;
POnClick: TNotifyEvent): IMyMenuItem;<br>
var<br>
LMenuItem: TMyTBMenuItem;<br>
begin<br>
LMenuItem := TMyTBMenuItem.Create(PParent.Owner);<br>
LMenuItem.Caption := PCaption;<br>
LMenuItem.OnClick := POnClick;<br>
Result := LMenuItem;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>procedure TMyTBMenuItem.MyFree;<br>
begin<br>
Free;<br>
end;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The intention of this is to allow you to dynamically create
menu items, but<br>
it doesn't matter if you have a normal menu (TMenuItem) or a<br>
Toolbar 2000 menu (TTBItem). You just deal with IMyMenuItem and the correct<br>
objects are created behind the scenes.</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>This works pretty well except I have an intermittent access
violations when freeing.</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>MyMenuItem: IMyMenuItem;</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>... // Do some stuff.</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>MyMenuItem := RootMenuItem.AddMenuItem('Hello
World', HelloWorldClick);</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>... // Later on</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>MMyMenuItem.MyFree; // Intermiitent access violation
here!</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I don't actually like the fact that I have MyFree. It was
the only way I could think of doing it at the time.</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Stacey</span></font><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>Stacey
Verner
Ph: +64-9-4154790<br>
Software Developer Fax:
+64-9-4154791<br>
DDI: +64-9-4154797<br>
CJN Technologies Ltd. Email: </span></font><a
href="mailto:stacey@cjntech.co.nz"><font size=2 face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New"'>stacey@cjntech.co.nz</span></font></a><br>
<st1:Street w:st="on"><st1:address w:st="on"><font size=2 face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New"'>PO Box 302-278, North</span></font></st1:address></st1:Street><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New"'>
Harbour, <st1:City w:st="on">Auckland</st1:City> 1330, <st1:country-region
w:st="on"><st1:place w:st="on">New Zealand</st1:place></st1:country-region><br>
<st1:Street w:st="on"><st1:address w:st="on">12 Piermark Drive, North</st1:address></st1:Street>
Harbour, <st1:place w:st="on"><st1:City w:st="on">Auckland</st1:City>, <st1:country-region
w:st="on">New Zealand</st1:country-region></st1:place><br>
Visit our website at </span></font><a href="http://www.cjntech.co.nz/"><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New"'>http://www.cjntech.co.nz/</span></font></a><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New"'>
</span></font><o:p></o:p></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
</div>
</body>
</html>