In Apple's delightful documentation of Chris Kane's Receptionist pattern (which 
I think of as a trampoline), the key method looks like this:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
        change:(NSDictionary *)change context:(void *)context {
    [queue addOperationWithBlock:^{
        task(keyPath, object, change);
    }];
}

https://developer.apple.com/library/mac/#documentation/General/Conceptual/CocoaEncyclopedia/ReceptionistPattern/ReceptionistPattern.html

Typically, "queue" is [NSOperationQueue mainQueue], our goal being to get 
ourselves back on the main thread in response to receiving a KVO notification 
that might have been sent on a background thread.

My question is simply this: in a world that has GCD, is there any reason why we 
wouldn't have "queue" be a GCD dispatch queue (probably the main queue) and 
call dispatch_asynch? Putting it even more generally (and this is probably my 
*real* question), is there any reason why I'd ever use NSOperationQueue's 
addOperationWithBlock given the existence of GCD?

Thx for your thoughts - m.


--
matt neuburg, phd = [email protected], http://www.apeth.net/matt/
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TidBITS, Mac news and reviews since 1990, http://www.tidbits.com



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