Reactive ExtensionsCommon scenarios for the use of Rx

Who am I?

• C# Developer

• 6 years working with C#

• 2 years using Rx

• joao.lvidal@gmail.com

• http://ca.linkedin.com/pub/john-vidal/73/33b/812/

• http://stackoverflow.com/users/1128106/j-lennon

Aim of this talk

• Reactive Extensions

• Reactive Programming

• Reactive Technology

• Reactive Scenarios

What’s Reactive Extensions

• Library

Used to:

• Real-time data

• Push notifications

• Asynchronous requests

• Event processing

Main goals:

• Unique interface

• Compose operations

• Good code

• Created by Microsoft in 2009

• Initially called LINQ To Events

• Turned into an Open Source Project 2 years ago

History of Rx

Rx Flavors

• RxPHP

• Rx.Py (for Python)

• Rx.Rb (for Ruby)

• RxJs (for JavaScript)

• RxCpp (for C++)

• Rx-Haskeel

• Rx-Pearl

• Rx-Java

• Mono

Reactive - What’s the Point?

• By Microsoft:

Reactive Extensions is for composing asynchronous and event-based programs using observable sequences and LINQ-style query operators.

• By Wikipedia:

Reactive Programming is a programming paradigm oriented around data flows and the propagation of change.

• By Reactive Manifesto:

Reactive Systems are Responsive, Elastic, Resilient, Message Driven.

Why Rx?

Specific Scenarios

• Real-time data• TCP/IP directly (duplex communication)

• Real-time web technologies (e.g. Polling, Server Side Events, WebSocket)

• Serial data (e.g. USB/RS 232)

*In .NET: WCF using duplex binding or SignalR.

• Push notifications• Mobile devices (e.g. IOS/Android/WP)

• Web browser extensions (e.g. Chrome/Firefox)

• Windows 8 apps

Common Scenarios

• Propagation of Change• If you need tell somebody that something happens. For example:

- Any kind of event-based, asynchronous-based, subscription-based, notification-based mechanism.

- Especially in combination or composition of more than one them

Common Apps

• Chat

• Stock Ticker

• Social Media

• Monitoring

• Games

• Dashboard

• Manufacturing

• Industrial Systems

• Event-driven Marketing

• Internet of Things

• Gestures (Kinect, Leap Motion)

References / To know more

Links:

• http://channel9.msdn.com/Tags/reactive+extensions

• http://www.introtorx.com/

• http://xgrommx.github.io/rx-book/

• http://reactconf.com/

• http://www.reactivemanifesto.org/

• http://www.infoq.com/reactive-extensions/

• http://blogs.msdn.com/b/rxteam/

People:

• Bart de Smet (Microsoft)

• Erik Meijer (Microsoft)

• Lee Campbell (IntroToRx)

• Jafar Hussain (Netflix)

• Jonathan Worthington

• James World

• Jim Wooley

• Dave Sexton

• Phil Haack

Thank You

Demo

Thank You

Bridges with Rx

• Event-based operations• Any kind of Binding (e.g. using patterns such as: MVVM, MVVMC, MVPVM)

*In .NET: event keyword (e.g. EventHandler delegate such as PropertyChangedEventHandler for INotifyPropertyChanged)

• Async-based operations• Callback / Promise / Future / Task

*In .NET: APM (IAsyncResult), EAP (EventNameCompleted += Handler), TAP (Task.Run(DoSomething)).

• Time-based operations• Scheduling / Timeout

Especially in combination or composition of one or more scenarios.

Who are using Reactive Extensions?

• 300.000+ downloads on Nuget.org (.NET Version)

• Netflix

• Microsoft Bing/Cortana/Azure

• GitHub Windows Client

• Hundreds of repositories in GitHub

• Dozens supporting http://reactivemanifesto.org with ribbons

The Major Interfaces

public interface IObservable<out T>

{

IDisposable Subscribe(IObserver<T> observer);

}

public interface IObserver<in T>

{

void OnCompleted(); // Notifies the observer that the source has finished sending messages.

void OnError(Exception error); // Notifies the observer about any exception or error.

void OnNext(T value); // Pushes the next data value from the source to the observer.

}

Reasons to use Rx

1. Avoid callback hell

2. Common interface to use in the code

3. Taming side-effects

Complexity

• Enumerable • 51 Operators

• EnumerableEx from Ix (Interactive Extensions)• 31 Operators

• Observable• 131 Operators

What’s a Reactive System?