Reacto

Reactive Programming for Ruby with some concurrency thrown into the mix!

How to install?

If you use bundler just add this line to your Gemfile:

gem 'reacto'

Alternatively you can install the gem with gem install reacto or clone this repository and play with it!

Why?

Because it is very cool to be reactive these days! Seriously - to be reactive means that your code is able to react on changes happening in various places right away. For example third party data sources or other parts of the code. It helps writing multi-component apps which could handle failures and still be available.

Of course there are other implementations of reactive programming for ruby:

• RxRuby : Very powerful implementation of RX. Handles concurrency and as a whole has more features than Reacto. So why Reacto? Reacto has simpler interface it is native Ruby lib and is easier to use it. The goal of Reacto is to be competitor to RxRuby in the ruby world. Still the author of Reacto is big fan of RX especially RxJava. He even has a book on the topic using RxJava : Learning Reactive Programming with Java 8
• Frappuccino : Very cool lib, easy to use and simply beautiful. The only drawback - it is a bit limited : no concurrency and small set of operators. But if you don't need more complicated operators it is the best. The author of Reacto highly recommends it.

Usage

Simple Trackables

The main entry point to the lib is the Reacto::Trackable class. It is something you can track for notifications. Usually A Reacto::Trackable implemenation is pushing notifications to some notification tracker. It depends on the source. We can have some remote streaming service as a source, or an synchronous HTTP request or some process pushing updates to another. Of course the source can be very simple, for example a single value:

  trackable = Reacto::Trackable.value(5)

This value won't be emitted as notification until there is no tracker (listener) attached to the trackable - so this trackable instance is lazy - won't do anything until necessary.

  trackable.on(value: ->(v) { puts v })

  # => 5

This line attaches a notification tracker to the trackable - a lambda that should be called when the trackable emits any value. This example is very simple and the trackable emits only one value - 5 when a tracker is attached to it so the lambda will be called and the value will be printed.

Programming Trackable behavior

A Reacto::Trackable can have custom behavior, defining what and when should be sent:

  trackable = Reacto::Trackable.make do |tracker|
    tracker.on_value('You say yes')
    tracker.on_value('I say no')

    sleep 1
    tracker.on_value('You say stop and I say go go go, oh no')
    tracker.on_close
  end

When a tracker is attached this behavior will become active and the tracker will receive the first two sentences as values, then, after one second the third one and then a closing notification.