lunacodegirl / signals

A micro-framework for creating and observing events.

Signals

Signals is a micro-framework for creating and observing events. It replaces delegates and NSNotificationCenter with something much more beautiful.

Features

• Fire-and-forget observation
• Type-safety
• Filtered observation
• Delayed and queued observation
• Comprehensive Unit Test Coverage

Requirements

• iOS 7.0+ / Mac OS X 10.9+
• Xcode 6.1+ (compatible with Swift 1.1 and 1.2)

Installation

1. Copy the Signal.swift file over to your project.
2. Done.

Quick start

Make events on a class observable by creating one or more signals:

class NetworkLoader {

    // Creates a number of signals that can be subscribed to
    let onData = Signal<(data:NSData, error:NSError)>()
    let onProgress = Signal<Float>()
    
    ...
    
    func receivedData(receivedData:NSData, receivedError:NSError) {
        // Whenever appropriate, fire off any of the signals
        self.onProgress.fire(1.0)
        self.onData.fire(data:receivedData, error:receivedError)
    }
}

Subscribe to these signals from elsewhere in your application

let networkLoader = NetworkLoader("http://artman.fi")

networkLoader.onProgress.listen(self) { (progress) in
    println("Loading progress: \(progress*100)%")
}

networkLoader.onData.listen(self) { (data, error) in
    // Do something with the data
}

Adding listeners to signals is a fire-and-forget operation. If your listener is deallocated, the Signal removes the listener from it's list of listeners. If the Signal emitter is deallocated, so is the closure that was supposed to fire on the listener, so you don't need to explicitly manage the removal of listeners.

Singals aren't restricted to one listener, so multiple objects can listen on the same Signal.

You can also subscribe to events after they have occurred:

networkLoader.onProgress.listenPast(self) { (progress) in
    // This will immediately fire with last progress that was reported
    // by the onProgress signal
    println("Loading progress: \(progress*100)%")
}

Signal listeners can apply filters:

networkLoader.onProgress.listen(self) { (progress) in
    // This fires when progress is done
}.filter { $0 == 1.0 }

You can queue up listener dispatches for a set amount of time and fire them only once:

networkLoader.onProgress.listen(self) { (progress) in
    // Executed once per second while progress changes
}.queueAndDelayBy(1.0)

Become more productive

Where delegates and notifications are too cumbersome and contain too much boilerplate, Signals is simple and modern.

Would you rather do this to implement a delegate:

• Create a protocol that defines what is delegated
• Create a delegate property on the class that wants to provide delegation
• Mark each class that wants to become a delegate as comforming to the delegate protocol
• Implement the delegate methods on the class that want to become a delegate
• Set the delegate property to become a delegate of the instance
• Check that you're delegate implements each delegate method before invoking it

Or do the same thing with Signals:

• Create a signal for the class that wants to provide an event
• Subscribe to the signal as a listener from any instance you want

Replace NSNotificationCenter

To replace global notifications via the NSNotificationCenter with Signals, just create a Singleton with a number of public signals that anybody can subscribe to or fire.

Communication

• If you found a bug, open an issue or submit a fix via a pull request.
• If you have a feature request, open an issue or submit a implementation via a pull request or hit me up on Twitter @artman
• If you want to contribute, submit a pull request.

License

Signals is released under an MIT license. See the LICENSE file for more information