How to set json response format from API on Rails 4?

Question

Ruby on Rails

You need to set the response format from the API in this form:

{
"errorCode": 0,
"errorMessage": "",
"result": [...]
}

At the moment, I wrote a helper in application_helper, to which I give either an error code and a message, or data.
Used in .jbuilder templates

def envelope(json, error_code=0, error_message='')
    json.errorCode error_code
    json.errorMessage error_message
    json.set! :result, [1] do
        yield if block_given?
    end
  end

Is there a better way, and if so, which one?