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响应式编程及框架
- 1. Reactive Programming and Framework Zhao Jie - SNDA - Sep. 2010
- 2. About me / / Jeffrey Zhao / Blog: http://blog.zhaojie.me/ Twitter: @jeffz_cn F#, Scala, JavaScript, Python, .NET, mono... Java (as the language) hater
- 3. What? Fundamentally change theway you think about coordinating and orchestrating asynchronous and event-based programming
- 4. Why? Because the essence of Cloud, Web, Mobile is asynchronous computations
- 5. How? By showing thatasynchronous and event-base computations are just push-based collections
- 6.
- 7. a := b+ c
- 8. Interactive Reactive Environment Program
- 9. Let’s implement both interfaces with...
- 11. Enumerable Collections interface IEnumerable<out T> { IEnumerator<T> GetEnumerator(); } interface IEnumerator<out T> { bool MoveNext(); T Current { get; } }
- 12. 1 Enumerator GetEnumerator() Current 3 2 MoveNext() Consumer pulls successive elements true/false from the collection
- 13. Dualize Enumerable Collections interface IEnumerable<out T> { // void -‐> enumerator IEnumerator<T> GetEnumerator(); } interface IObservable<out T> { // observer -‐> void IDisposable Subscribe(IObserver<T> o) }
- 14. Dualize Enumerable Collections interface IEnumerator<out T> { bool MoveNext(); // void -‐> bool T Current { get; } // void -‐> T // throws Exception } interface IObserver<in T> { void OnCompleted(bool done); // bool -‐> void T Current { set; } // T -‐> void void OnError(Exception ex); // accepts Exception }
- 15. Observable Collections interface IObservable<out T> { IDisposable Subscribe(IObserver<T> o) } interface IObserver<in T> { void OnCompleted(); void OnNext(T item); void OnError(Exception ex); }
- 16. 1 Observer Subscribe(o) 2 OnNext(e) 3 OnCompleted() Producer pushes successive elements X from the collection
- 17. IEnumerable & IEnumeratorare prototypical interfaces for interactive collections and interactive programs. IObservable & IObserver are prototypical interfaces for observable collections and reactive, asynchronous & event-based programs.
- 18.
- 19. Iterator / Observer Patterns in Java interface Iterable<T> { class Observable { Iterator<T> iterator(); void addObserver(Observer o); } void deleteObserver(Observer o); void deleteObservers(); int countObservers(); void notifyObservers(); void notifyObservers(Object arg); void setChanged(); void clearChanged(); boolean hasChanged(); } interface Iterator<T> { interface Observer { T next(); void update(Observable o, Object arg); } boolean hasNext(); void remove(); }
- 20.
- 21. LINQ to Observable If you are writing LINQ or declarative code in an interactive program...
- 22. LINQ to Observable If you are writing LINQ or declarative code in an interactive program... You already know how to use it!
- 23. ... the principlewe go by is, don't expect to see a particular concurrency model put into C# because there're many different concurrency model ... it's more about finding things are common to to all kinds of concurrency ... - Anders Hejlsberg
- 24. ... the principlewe go by is, don't expect to see a particular concurrency model put into C# because there're many different concurrency model ... it's more about finding things are common to to all kinds of concurrency ... - Anders Hejlsberg
- 25. LINQ to Object Standardquery operators Select Where SelectMany ... Extended query operators Zip Aggregate ...
- 26. LINQ to Observable Standardquery operators Select Where SelectMany ... Extended query operators Zip Throttle ...
- 27. How to movea ball by keyboard (ASDW)?
- 28. Imperative Impl. void OnKeyPress(object sender, KeyPressEventArgs e) { if (isPlaying) { if (e.KeyChar == 'a' && ball.Left > 0) { ball.Left -‐= 5; } else if (e.KeyChar == 'w' && ball.Top > 0) { ball.Top -‐= 5; } else ... } else ... }
- 29. Declarative Impl. // filter the KeyPress events when playing var keyPress = GetKeyPress().Where(_ => isPlaying); // filter the events to move left var moveLeft = from ev in keyPress where ev.EventArgs.KeyChar == 'a' where ball.Left > 0 select ev; moveLeft.Subscribe(_ => ball.Left -‐= 5); // filter the events to move top var moveTop = from ev in keyPress where ev.EventArgs.KeyChar == 'w' where ball.Top > 0 select ev; moveTop.Subscribe(_ => ball.Top -‐= 5);
- 30. Mouse drag anddraw
- 31. var mouseMove = GetMouseMove(); var mouseDiff = mouseMove.Zip(mouseMove.Skip(1), (prev, curr) => new { PrevPos = new Point( prev.EventArgs.X, prev.EventArgs.Y), CurrPos = new Point( curr.EventArgs.X, curr.EventArgs.Y) }); var mouseDrag = from _ in GetMouseDown() from diff in mouseDiff.TakeUntil(GetMouseUp()) select diff; mouseDrag.Subscribe(d => DrawLine(d.PrevPos, d.CurrPos));
- 32. Everything in Webis Asynchronous User actions AJAX requests Animations ...
- 33. Reactive Framework in JavaScript A full featured port for JavaScript Easy-to-use conversions from existing DOM, XmlHttpRequest, etc In a download size of less than 7kb (gzipped) Bindings for various libraries / frameworks jQuery MooTools Dojo ...
- 34. Mouse drag anddraw in JavaScript
- 35. var target = $("#paintPad"); var mouseMove = target.toObservable("mousemove"); var mouseDiff = mouseMove.Zip(mouseMove.Skip(1), function(prev, curr) { return { prevPos: { x: prev.clientX, y: prev.clientY }, currPos: { x: curr.clientX, y: curr.clientY } }; }); var mouseDown = target.toObservable("mousedown"); var mouseUp = target.toObservable("mouseup"); var mouseDrag = mouseDown.SelectMany(function() { mouseDiff.TakeUntil(mouseUp); }); mouseDrag.Subscribe( function(d) { drawLine(d.prevPos, d.currPos); });
- 36.
- 37. var textBox = $("#searchInput"); var searcher = textBox .toObservable("keyup") .Throttle(500) .Select(function(_) { return textBox.val(); }) .Select(function(term) { return queryWikipedia(term); }) .Switch(); searcher.Subscribe( function(data) { var results = $("#results"); results.empty(); $.each(data, function(_, value) { results.append($("<li/>").text(value)); }); }, function(error) { $("#error").html(error); });
- 38. Time flies likean arrow
- 39. var container = $("#container"); var mouseMove = container.toObservable("mousemove"); for (var i = 0; i < text.length; i++) { (function(i) { var ele = $("<span/>").text(text.charAt(i)); ele.css({position: "absolute"}).appendTo(container); mouseMove.Delay(i * 100).Subscribe(function (ev) { ele.css({ left: ev.clientX + i * 20 + 15 + "px", top: ev.clientY + "px" }); }); })(i);
- 40. Benefits of Rx Easyto composite and coordinate async operations Easy to express the algorithm (code locality) Easy to be unit tested ...
- 41. Rx & LanguageFeatures Features in C# that Rx uses Extension method Lambda expression & closure Type inference LINQ query expression Rx has been implemented in ... C# & VB JavaScript F#
- 42. Port to otherLanguages Rx can be easily ported to various languages Scala Ruby Python modern languages with basic functional features Almost impossible to implement Rx in Java Cannot extend a type without breaking code Missing enough functional features
- 43. Resources Matthew Podwysocki http://codebetter.com/blogs/matthew.podwysocki/ Reactive Framework on MSDN DevLabs http://msdn.microsoft.com/en-us/devlabs/ ee794896.aspx Tomáš Petříček http://tomasp.net/
- 44.