Real World

Functional

Reactive Programming

Hello!I am Eric Polerecky

You can find me at:

@detroitpro

Functional

Reactive

Programming

FRP is a HUGE topic; we are only going to scratch the surface. I’m not an expert in FRP

Is Rx (Reactive Extensions) right for me?

Rx (Rx.NET)

RxJs

Bacon.JS

Ruby

RxJava

RxCpp

Python

ReactiveCocoa

reactivex.io

rxmarbles.com

introtorx.com

The introduction to Reactive

Programming you've been

missing

Paul Betts - Introduction to

Rx

reactiveui.readthedocs.org

GitHub

NetFlix

Microsoft

Lets look a trivial example

DEM

O

OVERVIEWDEMO TIME!

Define FRP

Quick overview of functional programming

Dive into reactive programming

Why?!?!?

DEMO TIME!

REACTIVEReactive programming is an emerging

discipline which combines concurrency

and event-based and asynchronous

systems.

- Wikipedia

REACTIVE

Reactive programming is programming

with asynchronous data streams.

- staltz

TODO: Drink some water

Get example of async data streams from audience

FUNCTIONALLambda Calculus

Category Theory

Mondas

Functor

Parametric Polymorphism

FUNCTIONALLambda Calculus

Category Theory

Mondas

Functor

Parametric Polymorphism

FUNCTIONAL‘First Class’ FunctionsPass functions into function

Declarative ProgrammingCompose methods together to create higher abstraction

FRP uses come functional concepts but not all. FRP can be an introduction into functional

programming.

C# has functional concepts but is not a functional language.

FUNCTIONALvar even = numberRepository()

.Select(x => x + 1)

.Where(x => x % 2 == 0)

.OrderByDescending(x=>x);

linq is functional in nature

pass functions into ‘functions’ operators

methods can be composed

FUNCTIONAL‘First Class’ FunctionsPass functions into function

Declarative ProgrammingCompose methods together to create higher abstraction

Immutable DataWe don’t change data, we project (select) it into new formats

FRP only really uses a small subset of functional concepts. The reactive part of FRP is more more

complex and mind bending.

REACTIVE

Reactive programming is programming

with asynchronous data streams.

- staltz

TODO: Drink some water

Get example of async data streams from audience

REACTIVE

Click

Click: async - if it happens, it will happen in the future.

Examples of async data streams: click, message queue, mouse move.

FRP is CONSTRUCTS for programming with async data streams.

REACTIVEvariables

user input

properties

caches

lists

Things that are not async data streams; but should have been and can be made into async data

streams.

Anything that could change (mutate) it’s value

REACTIVEtwitter feed

directory

searching

web service calls

keyboard input

file changed

Twitter feed as data stream

When you start thinking about async data streams.

EVERYTHING BECOMES AN ASYNC DATA STREAM!

list scroll

video processing

mouse move

queues

messaging

REACTIVEtwitter feed

directory

searching

web service calls

keyboard input

file changed

This mental shift is the hardest part of FRP.

list scroll

video processing

mouse move

queues

messaging

REACTIVEIObservable<T> and IObserver<T>Sometime, in the future, someone is going to give me data, how do I reason about it

IEnumerable<T> and IEnumerable<T>I want all the data now! or I’ll stand here and wait, no one can do anything until I get my

data!

REACTIVEIObservable<T> and IObserver<T>Sometime, in the future, someone is going to give me data, how do I reason about it

IEnumerable<T> and IEnumerable<T>I want all the data now! or I’ll stand here and wait, no one can do anything until I get my

data!

REACTIVEEvents should have been lists

FRP is commonly called: Linq to events

REACTIVEIObservable<T>

Linq to events

+ Time!

REACTIVE

Reactive programming is turning

everything into an asynchronous data

stream and programming with

asynchronous data streams.

- Eric Polerecky aka: detroitproTODO: Drink some water

Get example of async data streams from audience

WHY?event soup

async / await everywhere!

test-ability

control time and space!

Lets look a non-trivial example

DEM

O

DECLARATIVE

PROGRAMMING

Higher abstraction, describe what you

want

Let’s talk about declarative programming

<h2>Hello</h2>

Let’s talk about declarative programming

var even = numberRepository()

.Select(x => x + 1)

.Where(x => x % 2 == 0)

.OrderByDescending(x=>x);

“

Expresses the logic of a

computation without describing its

control flow

=

Declarative Programming

What is a monad?

MyObservable //event args come in, I don’t care from where

.Select(x => x.FullPath) //transform data stream

.Do(ZipFile) //the business logic that needs to happen

.Catch<string,Exception>(...)

.Retry(3) //cross cutting concerns removed from logic

.Buffer(2) //bend time and space

.Subscribe(); //make it so

“

IObservable

=

Reversed IEnumerable + Time

“

Functional Reactive Programming

=

IObservable + Declarative

Programming

“

Functional Reactive Programming

is to events, lists and properties

what Inversion of Control is to

dependencies

WHENLets understand when to use Functional

Reactive Programming

ALWAYS!Just kidding...

Desktop/Mobile/UIresponsive UI

anywhere that is stateful

even the world wide web

Incoming Dataevents (click events)

streams of data (sensors)

http

file system

Let’s review what we learned about FRP

■ Reverse the flow of data

■ Declarative (higher level abstraction)

■ Linq to events

■ Good for when you would work with events

■ Good for when you have state (not request-response)

■ Reactive libraries are available in every language

■ Rx is on nuget (Rx-Main)

Thanks!Any questions?

You can find me at:

@detroitpro