ruby-grape/grape-on-rack

module Acme
  class PostPut < Grape::API
    cattr_accessor :rang

    format :json
    desc 'Returns pong.'
    get :ring do
      { rang: PostPut.rang }
    end
    post :ring do
      result = (PostPut.rang += 1)
      { rang: result }
    end
    params do
      requires :count, type: Integer, documentation: { param_type: 'body' }
    end
    put :ring do
      result = (PostPut.rang += params[:count].to_i)
      { rang: result }
    end
  end
end

Acme::PostPut.rang = 0