Rails render json including methods with parameters

Question

I have this render in a method controller:

render :json => @boats, :include => {:port => {:only => [:id, :name], :include => {:city => {:only => [:id, :name], :methods => :translatedCity}}}}

but translatedCity method in the model should accept language parameter.

  def translatedCity     
    language = params[:language]
    puts "translatedCity.language=" + language  
    city = TranslationService.translateCity(self.city_id, language)        
    return city.element_translation
  end

I have the parameter in the controller. Is there any way to pass this parameter to the method in the model?

Answer 1

Unfortunately the process of passing methods that require params to_json is not nicely built into rails. a typical pattern is to modify the as_json method on the model to accept custom keys, and then calling to_json (or render :json)

# city.rb model
def translatedCity(language)
  puts "translatedCity.language=" + language  
  city = TranslationService.translateCity(self.city_id, language)        
  return city.element_translation
end

def as_json(options = {})
  json_to_return = super
  if options.has_key? :translatedCity
    city_translation = self.translatedCity(options[:translatedCity][:language])
    json_to_return[:translatedCity] = city_translation
  end

  return json_to_return
end

now in your controller you pass everything in accoringdly

render :json => @boats, 
  :include => {
    :port => {
      :only => [:id, :name], 
      :include => {
        :city => {
          :only => [:id, :name], 
          :translatedCity => params[:language]
        }
      }
    }
  }

Answer 2

All answers are good!

I just did something like:

In controller:

boat.port.language = params[:language]

In model:

attr_accessor :language
  @language  

  def translatedCity            
    city = TranslationService.translateCity(self.city_id, language)        
    return city.element_translation
  end

What do you think?

Answer 3

as_json doesn't support methods that require arguments, but this is a good place to use a Presenter (or Decorator, or View Model, depending who you talk to) that builds the JSON you want. Draper is a gem that helps with that if you want one, and your controller would look something like

data = @boats.map do |boat|
  BoatPresenter.new(boat).as_json(language: params[:language])
end
render json: data

Then BoatPresenter would add the extra data you want in its as_json:

def as_json(options = {})
  @boat.as_json(options).tap do |json|
    json[:translated_city] = @boat.translated_city(options[:language])
  end
end

You can also have BoatPresenter add your default includes, etc. if you want a standard set without the controller having to worry about it. And if you don't want to do the array mapping yourself, Draper also offers collection presenters (eg BoatsPresenter).

---

If you're averse to adding a class, you could also override as_json directly on Boat to handle a language option:

def as_json(options = {})
  super(options).tap do |json|
    json[:translated_city] = translated_city(options[:language])
  end
end