Rails API versioning

api_constraints.rb

# lib/api_constraints.rb

class ApiConstraints
  def initialize(options)
    @version = options[:version]
    @default = options[:default]
    @domain = options[:domain]
  end

  def matches?(req)
    @default || req.headers['Accept'].include?("application/vnd.#{@domain}+json; version=#{@version}")
  end
end

api_steps.rb

# cucumber step for checking the API version

Given /^I send and accept JSON using version (\d+) of the (\w+) API$/ do |version, domain|
  header 'Accept', "application/vnd.#{domain}+json; version=#{version}"
  header 'Content-Type', 'application/json'
end

routes.rb

require 'api_constraints'

Rails.application.routes.draw do

  scope module: :v1, constraints: ApiConstraints.new(version: 1, default: :true, domain: APPLICATION_DOMAIN), defaults: {format: 'json'} do
    # resources . . .
  end

end