Re: Forwarding messages from an application delegate
Re: Forwarding messages from an application delegate
- Subject: Re: Forwarding messages from an application delegate
- From: Graham Cox <email@hidden>
- Date: Sat, 3 May 2008 00:44:29 +1000
You also need to override -respondsToSelector: and return a logical OR
of your delegate plus the old delegate's response, something like:
- (BOOL) respondsToSelector:(SEL) aSelector
{
BOOL responds = [super respondsToSelector:aSelector];
if( !responds )
responds = [[self oldDelegate] respondsToSelector:aSelector];
return responds;
}
Also, forwardInvocation isn't called unless your object has already
rejected the message, so its implementation should look like:
- (void) forwardInvocation:(NSInvocation*) invocation
{
SEL aSelector = [invocation selector];
if ([[self oldDelegate] respondsToSelector:aSelector])
[invocation invokeWithTarget:[self controller]];
else
[self doesNotRecognizeSelector:aSelector];
}
hth,
G.
On 3 May 2008, at 12:35 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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