Rx 101 - Tamir Dresher - Copenhagen .NET User Group
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Tamir Dresher presents an introduction to Reactive Extensions (Rx) which provides a framework for building asynchronous and event-based applications. Rx allows composing asynchronous and event-based programs using observable sequences and LINQ-style query operators. The presentation covers Rx core concepts like Observables and Observers, creating Observables, Rx queries, and managing concurrency using Schedulers.
![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-tamirdresher-160825214322/85/Rx-101-Tamir-Dresher-Copenhagen-NET-User-Group-37-320.jpg)
Rx 101 - Tamir Dresher - Copenhagen .NET User Group
- 1. 1 Tamir Dresher Senior Software Architect J Reactive Extensions 101
- 2. 222 • Software architect, consultant and instructor • Software Engineering Lecturer @ Ruppin Academic Center • Reactive Extensions in .NET (Manning) @tamir_dresher tamirdr@codevalue.net http://www.TamirDresher.com. About Me
- 3. Reactive Extensions Your headache relief pill to Asynchronous Event based applications Async Push Triggers Events
- 5. Social media IoT GPS External Services Your System So Many Sources…So Many Sources…
- 6. Agenda Rx building blocks – Observable and Observers Creating Observables Rx queries with Rx operators Managing Concurrency with Rx Schedulers 6
- 9. 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 ModelPull Model
- 10. ???? LoadMessages(string hashtag) { facebook.Search(hashtag); twitter.Search(hashtag); linkedin.Search(hashtag); } DoSomething( )msg Push ModelPush Model
- 11. Push model with Events 11 var mgr = new SocialNetworksManager(); mgr.MessageAvailable += (sender, msg) => {//do something}; mgr.LoadMessages("Rx"); class SocialNetworksManager { //members public event EventHandler<Message> MessageAvailable; public void LoadMessages(string hashtag) { var statuses = _facebook.Search(hashtag); NotifyMessages(statuses); : } } hard to unsubscribe non-composable can’t send as argument no isolation
- 12. ???? LoadMessages(string hashtag) { facebook.Search(hashtag); twitter.Search(hashtag); linkedin.Search(hashtag); } DoSomething( )msg Push ModelPush Model
- 13. observable observer Subscribe(observer) subscription OnNext(X1) OnNext(Xn) ⁞ ⁞ IDisposable Observables and ObserversObservables and Observers
- 14. OnCompleted() OnError(Exception) observable observer ⁞ Observables and ObserversObservables and Observers
- 15. 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(); } } InterfacesInterfaces
- 16. Rx packages 16
- 17. Push ModelPush Model with Rx Observables class ReactiveSocialNetworksManager { //members public IObservable<Message> ObserveMessages(string hashtag) { : } } var mgr = new ReactiveSocialNetworksManager(); mgr.ObserveLoadedMessages("Rx") .Subscribe( msg => Console.WriteLine($"Observed:{msg} t"), ex => { /*OnError*/ }, () => { /*OnCompleted*/ });
- 19. 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 PushPull To Push Subscribe function FacebookClient:
- 20. IObservable<Message> ObserveMessages(string hashtag) { } var messages = await GetMessagesAsync(hashtag); return messages.ToObservable(); Built-in ConvertersBuilt-in Converters Note: All observers will get the same emitted messages
- 21. IObservable<Message> ObserveMessages(string hashtag) { } return Observable.Defer( async () => { }); var messages = await GetMessagesAsync(hashtag); return messages.ToObservable(); Built-in ConvertersDefering the observable creation Note: Every observer will get the “fresh” emitted messages
- 22. Observable.Merge( facebook.ObserveMessages(hashtag), twitter.ObserveMessages(hashtag), linkedin.ObserveMessages(hashtag) ); Built-in OperatorsBuilt-in Combinators (combining operators)
- 23. 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 ⁞ Observables Factories
- 24. Observable Queries (Rx Operators)
- 25. 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 Rx operators
- 26. 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 ComposabilityComposability
- 27. g(x) f(x) Observable Query PipelineObservable Query Pipeline
- 29. 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 - RulesReactive Search - Rules
- 31. 31
- 32. 32 Where(s => s.Length > 2 )
- 33. 33 Where(s => s.Length > 2 ) Throttle(TimeSpan.FromSeconds(0.5))
- 34. 34 Where(s => s.Length > 2 ) Throttle(TimeSpan.FromSeconds(0.5)) DistinctUntilChanged()
- 35. 36 Select(text => SearchAsync(text)) “REA” “REAC” Switch() “REA” results are ignored since we switched to the “REAC” results
- 36. 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*/);
- 37. 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); });
- 38. Abstracting Time and Concurrency
- 39. What will be the output? The Repeat operator resubscribes the observer when the observable completes Most developers falsely believe that the program will immediately dispose the subscription and nothing will be written to the console Rx is not concurrent unless it explicitly told to The example above writes the sequence 1-5 indefinitely to the console 40 var subscription = Observable.Range(1, 5) .Repeat() .Subscribe(x => Console.WriteLine(x)); subscription.Dispose();
- 41. 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); }
- 42. // // 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 ConcurrencyParameterizing Concurrency
- 43. textChanged .Throttle(TimeSpan.FromSeconds(0.5), DefaultScheduler.Instance) .DistinctUntilChanged() .SelectMany(text => SearchAsync(text)) .Switch() .Subscribe(/*handle the results*/);
- 44. // // runs the observer callbacks on the specified // scheduler. // IObservable T ObserveOn<T>(IScheduler); // // runs the observer subscription and unsubsciption on // the specified scheduler. // IObservable T SubscribeOn<T>(IScheduler) Changing Execution ContextChanging Execution Context
- 45. textChanged .Throttle(TimeSpan.FromSeconds(0.5)) .DistinctUntilChanged() .Select(text => SearchAsync(text)) .Switch() .ObserveOn(DispatcherScheduler.Current) .Subscribe(/*handle the results*/); Changing Execution ContextChanging Execution Context
- 46. textChanged .Throttle(TimeSpan.FromSeconds(0.5)) .DistinctUntilChanged() .Select(text => SearchAsync(text)) .Switch() .ObserveOnDispatcher() .Subscribe(/*handle the results*/); Changing Execution ContextChanging Execution Context
- 47. Your headache relief pill to Asynchronous and Event based applications Async Push Triggers Events Reactive ExtensionsReactive Extensions
- 48. www.manning.com/dresher www.reactivex.io github.com/Reactive-Extensions Discount code: dreshermu Thank You
- 49. What will the following Console app print out? 51 http://landing.oz-code.com/CPH
Editor's Notes
- #3: My name is tamir dresher Im an architect from codevalue israel and a software engineering lecturer at the ruppin academic center CodeValue is a consulting company and we are also the proud development center of OzCode the amazing debugging extension for visual studio. We have a booth here at conference, so please go and check it out, youll be amazed how you lived without it. My book Rx in action is now available at Manning early access program should be published in the next few months. And that the end of my self promotion(it never hurts right?). So what are we really here for?
- #7: Breakpoints conditional breakpoints Comparing object while debugging Object IDs OzCode Compare Exceptions Breaking on exceptions Conditional exceptions break Debugging Multithreaded Applications Freezing debugging to the current thread detecting deadlocked tasks Using tracepoints Finding an object and seeing all object of certain type while debugging Debugging LINQ Post-mortum debugging Dumps
- #16: Since .net 4