Tamir Dresher - Reactive Extensions (Rx) 101
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Reactive applications are designed to handle asynchronous events in a way that maximizes responsiveness, resiliency and elasticity. Reactive Extensions (Rx) is a library created by Microsoft that abstracts away the sources of events and provides tools to handle them in a reactive way. With Rx, filtering events, composing event sources, transforming events and dealing with errors all become much simpler than with traditional tools. Reactive Extensions requires a mind change, thinking about your application as a message hub that knows how to react to messages.
![var $input = $('#input'),
$results = $('#results');
Rx.Observable.fromEvent($input, 'keyup')
.map(e => e.target.value)
.filter(text => text.length > 3)
.throttle(500 /* ms */)
.distinctUntilChanged()
.flatMapLatest(searchWikipedia)
.subscribe(data => {
var res = data[1];
$results.empty();
$.each(res, (_, value) => $('<li>' + value + '</li>').appendTo($results));
}, error => {
/* handle any errors */
$results.empty();
$('<li>Error: ' + error + '</li>').appendTo($results);
});](https://image.slidesharecdn.com/rx101-codemotionmilan2015-tamirdresher-headlines-151124162228-lva1-app6891/85/Tamir-Dresher-Reactive-Extensions-Rx-101-26-320.jpg)
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Tamir Dresher - Reactive Extensions (Rx) 101
- 1. MILAN 20/21.11.2015 Talk title: Reactive Extensions 101 Tamir Dresher – CodeValue - @tamir_dresher
- 2. • Software Architect, Consultant and Instructor • Software Engineering Lecturer @ Ruppin Academic Center @tamir_dresher [email protected] http://www.TamirDresher.com.
- 3. Your headache relief pill to Asynchronous and Event based applications Async Push Triggers Events Reactive Extensions
- 4. Reactive Programming concentrates on the propagation of changes and their effects simply put, how to react to changes and create dataflows that depend on them Reactive Programming
- 5. Social media IoT GPS External Services Your System So Many Sources…
- 8. IEnumerable<Message> LoadMessages(string hashtag) { var statuses = facebook.Search(hashtag); var tweets = twitter.Search(hashtag); var updates = linkedin.Search(hashtag); return statuses.Concat(tweets).Concat(updates); } Twitter App Linkedin Facebook Pull Model
- 9. ???? LoadMessages(string hashtag) { facebook.Search(hashtag); twitter.Search(hashtag); linkedin.Search(hashtag); } DoSomething( )msg Push Model
- 10. observable observer Subscribe(observer) subscription OnNext(X1) OnNext(Xn) ⁞ ⁞ IDisposable Observables and Observers
- 12. namespace System { public interface IObservable<out T> { IDisposable Subscribe(IObserver<T> observer); } public interface IObserver<in T> { void OnNext(T value); void OnError(Exception error); void OnCompleted(); } } Interfaces
- 14. IObservable<Message> ObserveMessages(string hashtag) { } return Observable.Create( async (o) => { }); var messages = await GetMessagesAsync(hashtag); foreach(var m in messages) { o.OnNext(m); } o.OnCompleted(); Pull To Push
- 15. IObservable<Message> ObserveMessages(string hashtag) { } return Observable.Defer( async () => { }); var messages = await GetMessagesAsync(hashtag); return message.ToObservable(); Built-in Converters
- 17. Observable.Range(1, 10) .Subscribe(x => Console.WriteLine(x)); Observable.Interval(TimeSpan.FromSeconds(1)) .Subscribe(x => Console.WriteLine(x)); Observable.FromEventPattern(SearchBox, "TextChanged")⁞ ⁞ 1 sec 1 sec Observables Factories ⁞
- 18. MILAN 20/21.11.2015 Observable Queries (Rx Operators)
- 19. Filtering Projection Partitioning Joins Grouping Set Element Generation Quantifiers Aggregation Error HandlingTime and Concurrency Where OfType Select SelectMany Materialize Skip Take TakeUntil CombineLatest Concat join GroupBy GroupByUntil Buffer Distinct DistinctUntilChanged Timeout TimeInterval ElementAt First Single Range Repeat Defer All Any Contains Sum Average Scan Catch OnErrorResumeNext Using
- 20. Operator2 Creates an IObservable<T3> IObservable parameters Operator 1 Subscribe( ) observer observable … Operator N Operator1 Creates an IObservable<T2> IObservable<T> Original source observer Subscribe Composability
- 22. Reactive Search
- 23. 1. At least 3 characters 2. Don’t overflow server (0.5 sec delay) 3. Don’t send the same string again 4. Discard results if another search was requested Reactive Search - Rules
- 25. Var textChanged = Observable.FromEventPattern(txt, “TextChanged”) .Select(_=>txt.Text); textChanged .Where(text=>text.Length>3) .Throttle(TimeSpan.FromSeconds(0.5)) .DistinctUntilChanged() .SelectMany(text => SearchAsync(text)) .Switch() .Subscribe(/*handle the results*/);
- 26. var $input = $('#input'), $results = $('#results'); Rx.Observable.fromEvent($input, 'keyup') .map(e => e.target.value) .filter(text => text.length > 3) .throttle(500 /* ms */) .distinctUntilChanged() .flatMapLatest(searchWikipedia) .subscribe(data => { var res = data[1]; $results.empty(); $.each(res, (_, value) => $('<li>' + value + '</li>').appendTo($results)); }, error => { /* handle any errors */ $results.empty(); $('<li>Error: ' + error + '</li>').appendTo($results); });
- 27. MILAN 20/21.11.2015 Abstracting Time and Concurrency
- 29. public interface IScheduler { DateTimeOffset Now { get; } IDisposable Schedule<TState>( TState state, Func<IScheduler, TState, IDisposable> action); IDisposable Schedule<TState>(TimeSpan dueTime, TState state, Func<IScheduler, TState, IDisposable> action); IDisposable Schedule<TState>(DateTimeOffset dueTime, TState state, Func<IScheduler, TState, IDisposable> action); }
- 30. // // Runs a timer on the default scheduler // IObservable TimeSpan // // Every operator that introduces concurrency // has an overload with an IScheduler // IObservable T TimeSpan IScheduler scheduler Parameterizing Concurrency
- 31. textChanged .Throttle(TimeSpan.FromSeconds(0.5), DefaultScheduler.Instance) .DistinctUntilChanged() .SelectMany(text => SearchAsync(text)) .Switch() .Subscribe(/*handle the results*/);
- 32. // // runs the observer callbacks on the specified // scheduler. // IObservable T T IScheduler // // runs the observer subscription and unsubsciption on // the specified scheduler. // IObservable T T IScheduler Changing Execution Context
- 33. textChanged .Throttle(TimeSpan.FromSeconds(0.5)) .DistinctUntilChanged() .SelectMany(text => SearchAsync(text)) .Switch() .ObserveOn(DispatcherScheduler.Current) .Subscribe(/*handle the results*/); Changing Execution Context
- 34. textChanged .Throttle(TimeSpan.FromSeconds(0.5)) .DistinctUntilChanged() .SelectMany(text => SearchAsync(text)) .Switch() .ObserveOnDispatcher() .Subscribe(/*handle the results*/); Changing Execution Context
- 36. Your headache relief pill to Asynchronous and Event based applications Async Push Triggers Events Reactive Extensions
- 37. Thank You www.manning.com/dresher www.reactivex.io github.com/Reactive-Extensions Discount code: ctwcodemot
- 38. MILAN 20/21.11.2015 - Tamir Dresher – Rx 101 Leave your feedback on Joind.in! https://m.joind.in/event/codemotion-milan-2015 Presenter contact details t: @tamir_dresher e: [email protected] b: TamirDresher.com w: www.codevalue.net