iphone - Implementing Delegate Pattern in Objective-C

Question

I am building a class that handles NSURLConnection requests. To allow other classes to use this class, I would like to allow the main class to call a delegate when connectionDidFinishLoading is fired.

I've looked through lots of documentation, but I can't find anything that gives any clear examples, and the code that I have doesn't call the delegate for some reason. The code I have so far is (code not relevant removed):

Interface:

@interface PDUrlHandler : NSObject {
id delegate;
}
- (void)searchForItemNamed:(NSString *)searchQuery;
@property (nonatomic, assign) id delegate;
@end
@interface NSObject (PDUrlHandlerDelegate) 
- (void)urlHandler:(PDUrlhandler*)urlHandler searchResultsFinishedLoading:(NSDictionary *)resultData;
@end

Implementation:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    NSLog(@"Fininshed Loading...");
    resultData = [self parseJSON:jsonData];

    if(delegate && [delegate respondsToSelector:@selector(urlHandler:searchResultsFinishedLoading:)]) {
        NSLog(@"Delegating!");
        [delegate urlHandler:self searchResultsFinishedLoading:resultData];
    } else {
        NSLog(@"Not Delegating. I dont know why.");
    }   

}

The delegate within the other class:

- (void)urlHandler:(PDUrlhandler*)urlHandler searchResultsFinishedLoading:(NSDictionary *)resultData;
{
    NSLog(@"Delegating!!!!");
}

Answer 1

My first thought was you might not have set the delegate, but you have. Other than that, the code looks correct. Can't see anything wrong. Did you try and put a breakpoint at the place where you are checking whether your delegate responds to a selector? Could be that the delegate value was not retained and became nil. Make sure your delegate is not nil and has the correct object.

Also are you sure the connection is asynchronous? Synchronous connections will not call the connectionDidFinishLoading method