PubSub-iOS

PubSub-iOS is a very simple, block based wrapper around NSNotificationCenter.

The goal is minimal syntax, strong typing, and automatic unregistering.

Here's what it looks like:

// Declare your notification
PubSub(nameChanged, NSString)

// Subscribe
[Sub while:self nameChanged:^(NSString* name){
    NSLog(@"New Name: %@", name);
}];

// Publish
[Pub nameChanged:@"Josh"];

Getting Started

This library has no dependencies and requires arc.

Copy 3 Files

Copy PubSub.h, PubSub.m, and Notifications.h into your XCode project. The PubSub files do all the work and Notifications.h is where you declare your notifications.

If your project doesn't have ARC enabled, add the -fobjc-arc flag for PubSub.m.

Import Notifications.h

In your AppName-Prefix.pch file, add #import "Notifications.h". This makes it available in all your classes. You can skip this step if you want to do it differently.

Declare your Notifications

In Notifications.h you will use a preprocessor statement to declare your notifications. Declare one per line. For example:

PubSub(nameChanged, NSString)

This generates two strongly typed methods that look kinda like this:

@interface Pub
+ (void) nameChanged:(NSString*)arg;
@end
@interface Sub
+ (void) while:(id)obj nameChanged:(void(^)(NSString*))callback;
@end

The first argument to PubSub is the name - it can be anything you want. The second argument is the type of object you are sending out.

Publishing

Now whenever you want to post a nameChanged notification, you just call:

[Pub nameChanged:@"Josh"];

Subscribing

When you want to subscribe to an event, you pass it the block of code that should run:

[Sub while:self nameChanged:^(NSString* name){
    NSLog(@"New Name: %@", name);
}];

The first argument while is the best part. It keeps a weak reference to an object. When that object goes away, the subscription is automatically cancelled. So "while" the object is not NULL, it subscribes.

For the most part you will pass self. That means when self goes away you are automatically unsubscribed. No cleanup necessary.

Compare that to NSNotificationCenter where you have to retain an observer then you have to explicitly unregister when you're done.