Re: Forwarding messages from an application delegate
Re: Forwarding messages from an application delegate
- Subject: Re: Forwarding messages from an application delegate
- From: Andy Lee <email@hidden>
- Date: Fri, 2 May 2008 10:53:46 -0400
Delegate methods aren't sent at all unless the delegate implements
them. I think your delegate is going to have to implement all
possible delegate methods and then forward them *if* the old delegate
implements them, and otherwise return an appropriate default value if
there is a return value.
This means the application will send all possible delegate methods to
you, as opposed to just the ones the old delegate implements, but
hopefully that won't cause any problems. I suppose you could do some
low-level hacking where you detect which methods the old delegate
implements and then remove unneeded methods from your delegate class.
--Andy
On May 2, 2008, at 10:35 AM, Matthew Gertner wrote:
Hi,
I am implementing an application delegate for a framework (Mozilla)
that already registers its own delegate internally. Ideally I would
like to be able to handle specific delegate messages in my class (in
this case adding items to the dock tile menu) and forward all other
invocations to the old delegate. So before I call [[NSApplication
sharedApplication] setDelegate] for my delegate, I retrieve the
existing delegate and save it in a member variable (mOldDelegate). I
thought that I could get invocations to forward automatically like
this:
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
if ([mOldDelegate respondsToSelector:[anInvocation selector]])
[anInvocation invokeWithTarget:mOldDelegate];
else
[super forwardInvocation:anInvocation];
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
if ([mOldDelegate respondsToSelector:aSelector])
return [mOldDelegate methodSignatureForSelector:aSelector];
else
return [super methodSignatureForSelector: aSelector];
}
For some reason neither methodSignatureForSelector nor
forwardInvocation is ever called. Perhaps this has something to do
with the way messages are sent to the delegate by the application. As
a result, my delegate never forwards to the old delegate. Any guidance
would be appreciated.
Matt
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