Often you want to observe a model object from multiple parts in your code. KVO can work, but I find it can get a mess. Using a listener protocol for each model makes it clear what can change, and who's listening.

DMListener offers an easy way to add listeners to your classes. It takes care of deallocation, so just add any view or controller as listener :)

Take a look at the example project, or BitStore where I'm using this in productive code.

Installation

If you're not using CocoaPods you'll find the source code files inside Pod/Classes.

Usage

A model class using DMListener would look like this:

#import <DMListener/DMListeners.h>

@implementation DMDemoModel {
    DMListeners* _listeners;
}

- (instancetype)init {
    if (self == [super init]) {
        _listeners = [[DMListeners alloc] init];
    }
    return self;
}

- (void)addListener:(id<DMDemoModelListener>)listener {
    [_listeners addListener:listener];
}

- (void)refreshData {
    [self performSelector:@selector(dataRefreshed) withObject:nil afterDelay:1.0];
}

- (void)dataRefreshed {
    [_listeners notifyListeners:^(id<DMDemoModelListener> listener) {
        [listener demoModelChanged:self];
    }];
}

@end

And to be notified of changes just call the addListener method:

DMDemoModel* model = [[DMDemoModel alloc] init];
[model addListener:self];

Take a look at the example project. You'll see a demo implementation inside DMAppDelegate.m

To run the example project you first have to run pod install from the Example directory.

Author

Dylan Marriott, [email protected]

License

DMListener is available under the MIT license. See the LICENSE file for more info.