Flip provides a declarative, layered way of enabling and disabling application functionality at run-time.
This gem optimizes for:
- developer ease-of-use,
- visibility and control for other stakeholders (like marketing); and
- run-time performance
There are three layers of strategies per feature:
- default
- database, to flip features site-wide for all users
- cookie, to flip features just for you (or someone else)
There is also a configurable system-wide default - !Rails.env.production?` works nicely.
Flip has a dashboard UI that's easy to understand and use.
Rails >= 4.0
# Gemfile
gem "flip"
# Generate the model and migration
> rails g flip:install
# Run the migration
> rake db:migrate
# Include the Feature model, e.g. config/initializers/feature.rb:
require 'feature'
# This is the model class generated by rails g flip:install
class Feature < ActiveRecord::Base
extend Flip::Declarable
# The recommended Flip strategy stack.
strategy Flip::CookieStrategy
strategy Flip::DatabaseStrategy
strategy Flip::DefaultStrategy
default false
# A basic feature declaration.
feature :shiny_things
# Override the system-wide default.
feature :world_domination, default: true
# Enabled half the time..? Sure, we can do that.
feature :flakey,
default: proc { rand(2).zero? }
# Provide a description, normally derived from the feature name.
feature :something,
default: true,
description: "Ability to purchase enrollments in courses"
endFlip.on? or the dynamic predicate methods are used to check feature state:
Flip.on? :world_domination # true
Flip.world_domination? # true
Flip.on? :shiny_things # false
Flip.shiny_things? # falseViews and controllers use the feature?(key) method:
<div>
<% if feature? :world_domination %>
<%= link_to "Dominate World", world_dominations_path %>
<% end %>
</div>The Flip::ControllerFilters module is mixed into the base ApplicationController class. The following controller will respond with 404 Page Not Found to all but the index action unless the :something feature is enabled:
class SampleController < ApplicationController
require_feature :something, :except => :index
def show
end
def index
end
endThe dashboard provides visibility and control over the features.
The gem includes some basic styles:
= content_for :stylesheets_head do
= stylesheet_link_tag "flip"You probably don't want the dashboard to be public. Here's one way of implementing access control.
app/controllers/admin/features_controller.rb:
class Admin::FeaturesController < Flip::FeaturesController
before_action :assert_authenticated_as_admin
endapp/controllers/admin/strategies_controller.rb:
class Admin::StrategiesController < Flip::StrategiesController
before_action :assert_authenticated_as_admin
endroutes.rb:
namespace :admin do
resources :features, only: [ :index ] do
resources :strategies, only: [ :update, :destroy ]
end
end
mount Flip::Engine => "/admin/features"You can optimize your feature to ensure that it doesn't make a ton of feature calls by adding Cacheable to your model.
extend Flip::CacheableThis will ensure that your features are eager loaded with one call to the database instead of every call to Flip#on? generating a call to the database. This is helpful if you have a larger Rails application and more than a few features defined.
To start or reset the cache, just call #start_feature_cache.
Created by Paul Annesley Copyright © 2011-2013 Learnable Pty Ltd, MIT Licence.
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