Append attributes to model object in Rails

Question

I have a Place model and a PlacesController. Currently the controller responds to JSON with certain objects. I would like to add more fields to the responded objects. For example, I would like to add every place's tags, queried by the method Place.tags.

I'm thinking in two solutions: convert the list of objects to a list of hashes and add the attributes that I want, or add a new column in the model, filling it in the controller iterating the list of objects. I'm not sure if there is a better way to do this.

I'm a bit confused; don't Places already have an association with their tags? — Dave Newton
– Dave Newton, Commented Feb 5, 2013 at 18:15

miked · Accepted Answer · 2013-02-05 18:17:42Z

5

I'm assuming:

 class Place < ActiveRecord:Base
   has_many :tags

If so, are you simply trying to add the associated tags to the place object's json? If so, you can use (where 'place' is a Place object):

 place.to_json(:include=>:tags)

answered Feb 5, 2013 at 18:17

miked

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1 Comment

Dave Newton Over a year ago

+1; this is the correct answer if the models are associated correctly (which they should be).

Community · Accepted Answer · 2017-05-23 11:44:32Z

1

You could use a template to generate the JSON as well. It will give you control over what appears in your JSON and is significantly faster than rendering via to_json or render :json.

Check out my question about the fastest way to render JSON here: What is the fastest way to render json in rails.

I've found RABL (https://github.com/nesquena/rabl) to be fast and easy to set up.

For your example, in RABL, you would do something like this:

class PlacesController < ApplicationController
  def show
    @place = Place.find(params[:id])
  end
end

And in the view:

object @place => :place
attributes :id, :name

children :tags => :tags do
  attributes :id, :name
end

edited May 23, 2017 at 11:44

CommunityBot

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answered Feb 5, 2013 at 18:24

John Naegle

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Comments

alexsanford1 · Accepted Answer · 2013-02-05 18:12:24Z

0

In this kind of situation I would probably use the presenter pattern. Take a look here: http://blog.jayfields.com/2007/03/rails-presenter-pattern.html

There's also a railscast if you have a pro account: http://railscasts.com/episodes/287-presenters-from-scratch

answered Feb 5, 2013 at 18:12

alexsanford1

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Jing · Accepted Answer · 2013-02-05 18:17:31Z

-1

I am not sure about my solution is the better way

# in controller
@place = Place.first
@place[:place_tags] = @place.tags.map(&:attributes)
render :json => @place

answered Feb 5, 2013 at 18:17

Jing

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