#NSObject+TIDelegateCommunications A category on NSObject to facilitate easy communication with a delegate
Tim Isted
http://www.timisted.net
Twitter: @timisted
##License NSObject+TIDelegateCommunications is offered under the MIT license.
##Summary
NSObject+TIDelegateCommunications is a category on NSObject to make it super easy to communicate with a delegate object.
Given a delegate protocol:
@protocol StuffFetcherDelegate <NSObject>
@optional
- (BOOL)stuffFetcherShouldFetchStuff:(TIStuffFetcher *)aStuffFetcher;
- (void)stuffFetcherStartedFetchingStuff:(TIStuffFetcher *)aStuffFetcher;
- (void)stuffFetcher:(TIStuffFetcher *)aStuffFetcher didFetchStuff:(id)stuff;
- (void)stuffFetcher:(TIStuffFetcher *)aStuffFetcher failedToFetchStuffWithIdentifier:(NSString *)anIdentifier error:(NSError *)error;
@end
The category lets you use this code:
id someStuff = blah;
[self ti_alertDelegateWithSelector:@selector(stuffFetcher:didFetchStuff:), someStuff];
or
[self ti_alertDelegateWithSelector:@selector(stuffFetcher:failedToFetchStuffWithIdentifier:error:), @"Identifier", anError];
without worrying about whether the delegate does or does not implement the method.
##Important Note that the category assumes the first argument is always the sender so you should not provide that argument.
If you need to call a delegate selector with the only argument being the object that sent it, use code like this:
[self ti_alertDelegateWithSelector:@selector(stuffFetcherStartedFetchingStuff:)];
The category makes use of invocations, so you can use it with selectors involving as many arguments as you like; the only requirement is that every argument is an object.
The code checks to make sure that the delegate responds to a selector; if it does, it creates an invocation and invokes it, otherwise it returns immediately, meaning you don't need to bracket your delegate calls in:
if( [[self delegate] respondsToSelector:@selector(dontNeedToDoThis:)] ) {
[[self delegate] dontNeedToDoThis:this];
}
Because the code uses invocations and involves NSMethodSignature's numberOfArguments method, you don't need to nil-terminate your arguments.
##Return Values
If you need to ask a delegate for a BOOL, you can do this:
BOOL returnValue = [self ti_boolFromDelegateWithSelector:@selector(stuffFetcherShouldFetchStuff:)];
If a method is optional, and you need the default behavior to be as if the method had returned YES, use the optimistic version:
BOOL returnValue = [self ti_optimisticBoolFromDelegateWithSelector:@selector(stuffFetcherShouldFetchStuff:)];
Similarly, if you need an object from a delegate:
id someObject = [self ti_objectFromDelegateWithSelector:@selector(stuffFetcherNecessaryObject:)];
##Main Thread To alert a delegate on the main thread, use this method:
- (void)ti_alertDelegateOnMainThreadWithSelector:(SEL)aSelector waitUntilDone:(BOOL)shouldWait, ...;
The variable arguments are the arguments to supply on the invocation (again, these should be objects).