iPhone: @protocol and @optional
iPhone: @protocol and @optional
- Subject: iPhone: @protocol and @optional
- From: John Michael Zorko <email@hidden>
- Date: Tue, 05 Jan 2010 10:53:55 -0800
Hello, all ...
After [re-]reading the Apple documentation, i'm still not clear as to what @optional really does in a @protocol. I thought that declaring certain messages as @optional would make the app not crash if a certain message didn't have an implementation in a class that adopts the protocol, however i'm finding that this isn't the case:
2010-01-05 10:40:58.698 VoxityNowPlaying[14413:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[VoxityNowPlayingViewController playerURLFinished:]: unrecognized selector sent to instance 0x39138f0'
... yet my protocol is defined thusly:
@protocol VoxityPlayerDelegate <NSObject>
@optional
- (void)playerURLFinished:(NSURL *)url;
.
.
.
@end
Do I need to wrap code that sends messages to delegates with -respondsToSelector? If so, what is the point of @optional in the protocol?
Regards,
John
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