Exposure Fail -

get_metric_controller.rb

# Controller
module Web::Controllers::Home
  class GetMetric
    include Web::Action
    expose :method_to_use, :query_string
    handle_exception ArgumentError => :handle_no_query_string


    def call(params)
      raise ArgumentError.new('Failed to provide parameters') if params.env["QUERY_STRING"].empty? 
      raise ArgumentError.new('Failed to provide named metric') unless valid_query_string?
      @method_to_use = "get_total_managed"
      @query_string = { :start_date => '2015-01-01', :end_date => '2015-02-01' }
    end

    private
    def handle_no_query_string(exception)
      status 400, exception.message
    end

    def valid_query_string?
      params.env["QUERY_STRING"].include?('metric=')
    end
  end
end

get_metric_view.rb

# View 
module Web::Views::Home
  class GetMetric
    include Web::View
    format :json

    def render
      result = MetricRepository.raw_all(method_to_use, query_string)
      result = { :meta_data => [ :total => result[0][:total], :period => '2015-01-01_to_2015-02-01'] }
      result
    end
  end

  Web::Views::Home::GetMetric.render(format: :json)
end