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Ruby

View the full source code at https://github.com/growthbook/growthbook-ruby.

Installation​

Install the gem

gem install growthbook

Quick start​

require 'growthbook'
require 'uri'
require 'net/http'
require 'json'

# Fetch features from GrowthBook API (or a Redis cache, etc.)
uri = URI('https://cdn.growthbook.io/api/features/MY_API_KEY')
res = Net::HTTP.get_response(uri)
features = res.is_a?(Net::HTTPSuccess) ? JSON.parse(res.body)['features'] : nil

# Create a context for the current user/request
gb = Growthbook::Context.new(
  features: features,
  # User attributes for targeting / variation assignment
  attributes: {
    id: '123',
    country: 'US'
  }
)

# Use a boolean feature flag
if gb.on? :my_feature_key
  puts 'My feature is on!'
end

# Get the value of a multivariate feature with a fallback
btn_color = gb.feature_value(:signup_btn_color, 'pink')

Track experiment impressions​

When a feature's value is determined by an experiment (A/B test), you typically want to track that assignment event for later analysis.

There are two ways to do this. First is by accessing all impressions at the end of a request:

gb.impressions.each do |key, result|
  puts "Assigned variation #{result.variation_id} in experiment #{key}"
end

Second is by using a listener to get alerted in realtime as users are put into experiments:

class MyImpressionListener
  def on_experiment_viewed(experiment, result)
    puts "Assigned variation #{result.variation_id} in experiment #{experiment.key}"
  end
end

gb.listener = MyImpressionListener.new

Using with Rails​

The recommended way to use GrowthBook with a Rails app is as follows:

  1. Fetch the features from the GrowthBook API (or a cache) once at server startup
  2. At the start of each request, create a new Context object
  3. Use the Context object to evaluate features and run experiments during the request
  4. At the end of a request, track experiment impressions (if any) and destroy the Context instance
  5. (optional) Periodically refresh the list of features from the GrowthBook API in the background

Dev and QA helpers​

For dev/QA it's often useful to force specific feature values.

# These take precedence over everything else when determining a feature's value
gb.forced_features = {
  my_feature: true,
  other_feature: "new value"
}

# Will always be true
gb.is_on?(:my_feature)

# Will always be "new value"
gb.feature_value(:other_feature)

For more predictability during QA, you can also globally disable all random assignment in experiments from running:

gb.enabled = false

Inline experiments​

It's also possible to directly run an experiment directly in code without going through a feature flag.

# Simple 50/50 experiment
result = gb.run(Growthbook::InlineExperiment.new(
  key: "my-experiment-key",
  variations: ["red", "green"]
))

# Whether or not the user was included in the experiment (either true or false)
puts(result.in_experiment ? 'included' : 'excluded')

# The value of the assigned variation (either "red" or "green")
puts(result.value)

# The variation index (either 0 or 1)
puts(result.variation_id)

There are lots of additional options when running inline experiments:

gb.run(Growthbook::InlineExperiment.new(
  key: "my-experiment-key",
  variations: ["red", "green"],
  # Filter by context attributes
  condition: {
    country: {
      "$in": ["US", "CA"]
    }
  },
  # Adjust variation weights from the default 50/50 split
  weights: [0.8, 0.2],
  # Run for a subset of traffic (0 to 1, default = 1)
  coverage: 0.5,
  # Use a different context attribute for assigning a variation (default = "id")
  hash_attribute: "device_id",
  # Use a namespace to run mutually exclusive experiments
  namespace: ["pricing-page", 0, 0.25]
))

Code Examples​