Purpose

FXNotifications is a category on NSNotificationCenter that provides an improved block-based API that is simpler and easier to use, and avoids the various retain cycle and memory leak pitfalls of the official API.

For more details, see this article: http://sealedabstract.com/code/nsnotificationcenter-with-blocks-considered-harmful/ and this gist: https://gist.github.com/nicklockwood/7559729

Supported iOS & SDK Versions

• Supported build target - iOS 7.0 / Mac OS 10.9 (Xcode 5.0, Apple LLVM compiler 5.0)
• Earliest supported deployment target - iOS 5.0 / Mac OS 10.7
• Earliest compatible deployment target - iOS 5.0 / Mac OS 10.7

NOTE: 'Supported' means that the library has been tested with this version. 'Compatible' means that the library should work on this iOS version (i.e. it doesn't rely on any unavailable SDK features) but is no longer being tested for compatibility and may require tweaking or bug fixes to run correctly.

ARC Compatibility

FXNotifications requires ARC and uses weak references.

Thread Safety

It is safe to add and remove observers concurrently on different threads using the FXNotification methods. Callback blocks will be executed on the specified queue.

Installation & Usage

To use FXNotifications, just drag the FXNotifications.h and .m files into your project and import the header file in your class.

Methods

FXNotifications extends NSNotificationCenter with a single method

- (void)addObserver:(id)observer
            forName:(NSString *)name
             object:(id)object
              queue:(NSOperationQueue *)queue
         usingBlock:(void (^)(NSNotification *note, __weak id observer))block;

This method is a hybrid of the two built-in notification observer methods. The observer parameter is required, and represents the owner of the block argument. When the observer is released, the block will be released as well.

The name, object, queue and block arguments work as they do in the normal block-based observer method. The queue parameter defaults to [NSOperationQueue currentQueue] if nil. To avoid retain cycles in your block, you can refer to the weak observer parameter that is passed as a second argument.

There is no token value returned; to stop observing the notification, use the standard -removeObserver: or -removeObserver:name:object: methods of NSNotificationCenter. There is no need to call removeObserver: in the observer's dealloc method; this is done automatically.

An typical usage might be:

[[NSNotificationCenter defaultCenter] addObserver:self
                                          forName:NSSomeNotificationName
                                           object:nil
                                            queue:[NSOperationQueue mainQueue]
                                       usingBlock:^(NSNotification *note, __weak id observer) {
                                                      NSLog(@"self: %@", observer); // look, no leaks!
                                                  }];