Now You're Thinking With Signals!

A ReactiveCocoa Adventure

Who is this guy?

Jeames BoneiOS Software Engineer @ Outware Mobile@jeamesbone on all the things.

FunctionalReactive

Programming

What is FRP?

F for Functional

Immutable Stateless

R for Reactive

What instead of how Derived stateInstead of telling a computer how to do its job, why don't we just tell it what it's job is and let it figure the rest out?

Functional Reactive Programming Combines functional and reactive paradigms. Uses streams of values and transformations on streams to

derive state.

Why FRPUIs are big, messy, mutable, stateful bags of sadness. Reduce mutable state Simpler programs Better code

ReactiveCocoa

Signals

Events

public enum Event { /// A value provided by the signal. case Next(T)

/// The signal terminated because of an error. No further events will be /// received. case Error(E)

/// The signal successfully terminated. No further events will be received. case Completed

/// Event production on the signal has been interrupted. No further events /// will be received. case Interrupted}

Signals

Signals in ReactiveCocoa 3

Signal

Signals model an existing stream of events in your app. User input Notifications Location Updates

SignalProducers

SignalProducer

SignalProducers model the results of some work. Network requests A modal view A watch connectivity request

Errors

Errors are passed on to the next step in the stream. If any point of the stream fails, we can handle this in one

place. Railway oriented programming

OperatorsTo the internet!

Example

let searchStrings = textField.rac_textSignal() .toSignalProducer() .map { text in text as! String }

let searchResults = searchStrings .flatMap(.Latest) { query in let URLRequest = self.searchRequestWithEscapedQuery(query) return NSURLSession.sharedSession().rac_dataWithRequest(URLRequest) } .map { data, URLResponse in let string = String(data: data, encoding: NSUTF8StringEncoding)! return parseJSONResultsFromString(string) } .map { JSONResults in return self.parseModelFromJSON(JSONResults) } .observeOn(UIScheduler())

searchResults.start(next: { model in self.updateUIWithModel(model)})

Now for magic

let searchResults = searchStrings .flatMap(.Latest) { query in let URLRequest = self.searchRequestWithEscapedQuery(query) return NSURLSession.sharedSession().rac_dataWithRequest(URLRequest) .retry(3) .catch { error in self.displayError(error) return SignalProducer.empty } } .map { data, URLResponse in let string = String(data: data, encoding: NSUTF8StringEncoding)! return parseJSONResultsFromString(string) } .map { JSONResults in return self.parseModelFromJSON(JSONResults) } .observeOn(UIScheduler())

But wait there's more!

let searchStrings = textField.rac_textSignal() .toSignalProducer() .map { text in text as! String } .filter { text in text.characters.count > 4 } .throttle(0.5, onScheduler: QueueScheduler.mainQueueScheduler)

What has this given us?

Less code Maintainable code Readable code

Where to next? http://reactivecocoa.io/ Try it!

Thanks!Questions?