Question

I have this piece of code:

- (id) getSearchSuggestions:(NSString*)q;
- (NSOperationQueue*) getSearchSuggestions:(NSString*)q callback:(id<UserDelegate>)callback;
- (id) getSearchSuggestions;
- (NSOperationQueue*) getSearchSuggestions:(id<UserDelegate>)callback;

And I Xcode keeps showing me an error on the last line:

Duplicate declaration of method "getSearchSuggestions"

Why? It seems to me that the signatures are all different.

Answer 1

This signature:

- (id) getSearchSuggestions:(NSString*)q;

Is identical to this signature:

- (NSOperationQueue*) getSearchSuggestions:(id<UserDelegate>)callback;

All object pointers are id. So both of these are methods that take an object and return an object.

Examples of better names would be:

- (id)searchSuggestionsForQueryString:(NSString*)q; // Or ForTag, or whatever "q" is
- (NSOperationQueue*)searchOperationQueueForQuery:(NSString*)q callback:(id<UserDelegate>)callback;
- (id)fetchSearchSuggestions;
- (NSOperationQueue*)searchOperationQueueWithCallback:(id<UserDelegate>)callback;

It’s not exactly clear why you return an operation queue here, but this is the kind of name you’d use for a method that did that.