API rails constraint

app-constraints-api_constraint.rb

class ApiConstraint
  attr_reader :version

  def initialize(options)
    @version = options.fetch(:version)
  end

  def matches?(request)
    request
      .headers
      .fetch(:accept)
      .include?("version=#{version}")
  end
end

config-routes.rb

Rails.application.routes.draw do

  namespace :api, path: "/", constraints: { subdomain: "api" }, format: :json do
    scope module: :v1, constraints: ApiConstraint.new(version: 1) do
      # Put your v1 controllers here
    end
  end
end