Sample Grape/Swagger Cat API

config.ru

require './main'

run API::Root

main.rb

require 'bundler/setup'
Bundler.require(:default)

module API
  module Entities
    class Pajamas < Grape::Entity
      expose :id,    documentation: {type: 'integer'}
      expose :color, documentation: {type: 'string', desc: 'The color'}
    end

    class Cat < Grape::Entity
      expose :id,      documentation: {type: 'integer'}
      expose :name,    documentation: {type: 'string', desc: "The cat's name"}
      expose :pajamas, using: API::Entities::Pajamas,
                       documentation: {type: 'API::Pajamas', desc: "The cat's pajamas"}
    end
  end

  class Cats < Grape::API
    version 'v1'
    
    get :cats,
      http_codes: [[200, 'Ok', API::Entities::Cat]] do
      present [], with: API::Entities::Cat
    end
  end
    
  class Root < Grape::API
    before do 
      header['Access-Control-Allow-Origin'] = '*'
      header['Access-Control-Request-Method'] = '*'
    end
    mount API::Cats
    add_swagger_documentation
  end 
end