Ruby SDK for featureflow
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Ruby SDK for featureflow

Featureflow Ruby SDK

Get your Featureflow account at

Get Started

The easiest way to get started is to follow the Featureflow quick start guides

Change Log

Please see CHANGELOG.


Getting Started


Add the following line to your Gemfile

gem 'featureflow'

Requiring featureflow in your ruby application will expose the classes Featureflow::Client, Featuerflow::UserBuilder and Featureflow::Feature.

The usage of each class is documented below.

Quick start

Firstly you will need to get your environment's Featureflow Server API key and initialise a new Featureflow client

This will load the rules for each feature for the current environment, specified by the api key. These rules can be changed at https://<your-org-key> When the rules are updated, the changes made will be applied to your application.

Ruby Quick Start

If you are using ruby you can create a featureflow client like this:

featureflow = api_key: '<Your server api key goes here>'

Or, you can set the environment variable FEATUREFLOW_SERVER_KEY and just write:

featureflow =

Note: featureflow, as instantiated above, should be treated as a singleton. You are responsible for sharing it with the rest of your application

Rails Quick Start

If you are using rails you can run the generator to setup Featureflow in your Rails application.

$ rails generator featureflow <Your server api key goes here>

Or, you can set the environment variable FEATUREFLOW_SERVER_KEY and the Rails Featureflow client will pick it up and use that.

You will then be able to access your Featureflow client in your controllers, for example:

class MainController < ApplicationController
  def index
    featureflow # this method will now reference the featureflow client

Defining a User

Before evaluating a feature you must define a user.
Featureflow uses users to target different user groups to specific feature variants. A featureflow user has an id, which should uniquely identify the current user, and optionally additional attributes. Featureflow requires the user id to be unique per user for gradual rollout of features.

There are two ways to define a user:

require 'featureflow'
user_id = '<unique_user_identifier>'

# option 1, use the user builder
user =
                                     .with_attributes(country: 'US',
                                                  roles: %w[USER_ADMIN, BETA_CUSTOMER])

# option 2, use just a string
user = user_id

Evaluating Features

In your code, you can test the value of your feature using something similar to below For these examples below, assume the feature my-feature-key is equal to 'on' for the current user

if featureflow.evaluate('my-feature-key', user).is? 'on'
  # this code will be run because 'my-feature-key' is set to 'on' for the given user

Because the most common variants for a feature are 'on' and 'off', we have provided two helper methods .on? and .off?

if featureflow.evaluate('my-feature-key', user).on?
  # this feature code will be run because 'my-feature-key' is set to 'on'

if featureflow.evaluate('my-feature-key', user).off?
  # this feature code won't be run because 'my-feature-key' is not set to 'off'

Pre-registering Features

Featureflow allows you to pre-register features that may not be defined in your Featureflow project to ensure that those features are available when that version of your code is running. If in the off-chance your application is unable to access the Featureflow servers and you don't have access to a cached version of the features, you can specify a failover variant for any feature.

The failover variant allows you to control what variant a feature will evaluate to when no rules are available for the feature. If a failover variant isn't defined, each feature will use a default feailover variant of 'off'.

You can pre-register features at the initialisation of your featureflow client like below:

require 'featureflow'

FEATUREFLOW_SERVER_KEY = '<Your server api key goes here>'

                                      with_features: [
                                        Featureflow::Feature.create('key-one', 'on'),
                                        Featureflow::Feature.create('key-three', 'custom'),

# ... app has been started offline
featureflow.evaluate('key-one', user).on? # == true
featureflow.evaluate('key-two', user).off? # == true
featureflow.evaluate('key-three', user).is? 'custom' # == true

Further documentation

Further documentation can be found here


  • Write documentation
  • Release to RubyGems
  • Write Ruby on Rails integration
  • Add Ruby on Rails helper to user featureflow in views



#Developer documentation

To build and test the SDK

rvm install 2.5.1
rvm use --default 2.5.1
bundle install
ruby test.rb