Thank you very much Graham!
Looks just like what I was looking for.
Eyal
On Jul 19, 2009, at 3:46 PM, Graham Cox wrote:
On 19/07/2009, at 10:06 PM, Eyal Redler wrote:
This works fine but it requires me to write an annoying amount such
glue code every time I add an action so I'm looking for a better
way to do this. Is it possible to further delegate the action
methods and menu validation from the NSDocument subclass? The best
way for me would be to have internalObject implement
validateMenuItem and myAction and have the NSDocument pass them
along without actually implementing each action method.
It sure is - use invocation forwarding. You need to override the
following NSObject methods:
- (NSMethodSignature *) methodSignatureForSelector:(SEL) aSelector;
- (BOOL) respondsToSelector:(SEL) aSelector;
- (void) forwardInvocation:(NSInvocation*) invocation;
The first two methods should query the object you're devolving to
when super returns nil and NO respectively, and the third should
invoke the invocation on the new target. The result is that the
target object can act as if it were directly being targeted by the
original command (action) and even implement its own
validateMenuItem: etc.
More on this here: http://www.cocoadev.com/index.pl?NSInvocation
It's hard to find in the Apple documentation so I was unable to
immediately find the right page there, but it's in there somewhere.
For example, I have a target object referred to as "active layer"
and this code exists in my view's controller:
- (void) forwardInvocation:(NSInvocation*) invocation
{
SEL aSelector = [invocation selector];
if ([[self activeLayer] respondsToSelector:aSelector])
[invocation invokeWithTarget:[self activeLayer]];
else
[self doesNotRecognizeSelector:aSelector];
}
- (NSMethodSignature *) methodSignatureForSelector:(SEL) aSelector
{
NSMethodSignature* sig;
sig = [super methodSignatureForSelector:aSelector];
if ( sig == nil )
sig = [[self activeLayer] methodSignatureForSelector:aSelector];
return sig;
}
- (BOOL) respondsToSelector:(SEL) aSelector
{
return [super respondsToSelector:aSelector] || [[self activeLayer]
respondsToSelector:aSelector];
}
hope this helps,
--Graham
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