gistfile1.rb

class CustomerAPI < Grape::API
  version 'v1', :using => :header

  rescue_from ActiveRecord::RecordInvalid do |e|
    # Precondition Failed
    error_response(:status => 412, :message => { :error => e.message }.to_json)
  end

  helpers do
    def authenticate!
      error!('Unauthorized', 401) unless env['HTTP_AUTHORIZATION'] == 'letmein'
    end
  end

  resource :users do
    before { authenticate! }

    desc "Create a user"
    post :create do
      User.create!(params[:user]).to_json
    end
  end
end