Mongoid virtual attributes in to_json - ruby-on-rails

I'm trying to get some virtual (non-persisted) attributes to show up in the JSON representation of some Mongoid models, but can't seem to get it to work:
class MyModel
include Mongoid::Document
def virtual_attribute
#my_attribute || false
end
def virtual_attribute=(value)
#my_attribute=value
end
end
class MyController
def myaction
false_values=MyModel.where( whatever )
true_values=MyModel.where( something_else ).map{ |model| model.virtual_attribute=true }
#val['my_models']=false_values+true_values
render json: #val.to_json( :include => {:my_models => {:methods => %w(virtual_attribute)}} )
end
end
virtual_attribute doesn't appear in the json. What am I doing wrong?
Edit - ok, so I guess my actual problem is that I can't figure out how to invoke the virtual_attribute method on each of an array of objects that is nested in the root object.

to_json passes the options directly to the array and the objects. :include is only a Mongoid thing:
render json: #val.to_json(methods: :virtual_attribute)

Related

Including virtual attributes when responding_to a JSON call

I have a post model that has a virtual attribute that I would like to set and then include in a response to a JSON call to my post#index action. I can't seem to get the virtual attribute to be included in the response.
class Post < ActiveRecord::Base
attr_accessible :height
attr_accessor :m_height
end
class PostsController < ApplicationController
respond_to :html, :json, :js
def index
story = Story.find(params[:story_id])
#posts = story.posts.where("posts.id >= ?", 100)
#posts.each do |post|
post.m_width = post.height * 200
end
results = { :total_views => story.total_views,
:new_posts => #posts }
respond_with(results)
end
end
I think that I must need something similar to #post.to_json(:methods => %w(m_width)), but I don't see how to use :methods in a respond_with
This seems to provide the answer. Implement a to_json and to_xml in your models, as appropriate, with definitions like:
There's a better answer implied here.
Following code stolen from the post:
def as_json(options={})
super(options.merge(:methods => [...], :only => [...], :include => [...])
end
to_json won't be called on your model in this case, from what I can tell in the source, but as_json will be, in the process of serialization.
So, here's what happens, in overview form:
You call respond_with with the results hash you've constructed.
Rails (ActionController) calls to_json on that.
to_json sends you over to JSON::Encoding which keeps calling as_json all the way down until everything is JSONified.
That's why there was the confusion about to_json and as_json in an earlier version of this answer.

Rails as_json with two unrelated models

Given two models and a controller:
Apples
class Apples < ActiveRecord::Base
belongs_to :not_oranges
...
def as_json(options={})
opts = {:include => [:not_oranges]}
super(options.reverse_merge! opts)
end
end
Oranges
class Oranges < ActiveRecord::Base
belongs_to :not_apples
...
def as_json(options={})
opts = {:include => [:not_apples]}
super(options.reverse_merge! opts)
end
end
Search Controller
class SearchController < ApplicationController
a = Apples.search params[:q]
o - Oranges.search params[:q]
#results = {
:apples => a,
:oranges => o
}
respond_to do |format|
format.json { render :json => #results }
end
As you can see, the two models are completely unrelated and both have different :include options in their as_json definitions.
All works as expected if the search query only hits apples or only hits oranges, but once both objects aren't empty I get:
undefined method `not_apples' for #<Oranges:0x00000004af8cd8>
Seems either the two as_json definitions are being merged, or Oranges.as_json is being overriden by Apples.as_json.
Is this expected behaviour? Is there any clean way around it without using something like RABL? I feel it would be overkill for my needs.
In pseudo code the code for hash as_json method looks like
def as_json(options={})
Hash[collect {|key,element| [key.to_s,element.as_json(options)]}]
end
But your element is modifying the options argument you pass to it. Hash is unaware of this and so passes the modified options hash to as json.
It's usually a good idea not to modify in place the arguments passed to you, except when it is very clear this is ok. I'd rewrite your method as
def as_json(options={})
defaults = {:include => :not_apples}
super(defaults.merge(options))
end

Including a virtual attribute in the respond_with hash

I am trying to include a virtual attribute/method within a respond_to JSON hash.
The Model (employee.rb)
attr_reader :my_method
def my_method
return "foobar"
end
The Controller (employees_controller.rb)
respond_to :json
def index
#employees = Employee.all
respond_with(:data => #employees, :total => Employee.all.count)
end
It is important that I have "data" as the json root for the collection of "employees" and also to include the "total" within the hash. This works well and returns a nice JSON result of all the employees and the total value.
My qustion is: How do I include the virtual attribute "my_method" for each employee within the employees hash in the JSON response?
Thanks for your time!
This is what worked for me.
Employee.rb
def as_json(options={})
super.as_json(options).merge({:my_method => my_method})
end
Thanks for cmason for pointing me in the right direction. Any other solutions are welcome.
In Rails 3 one can use following
#yourmodel.to_json(methods: ['virtual_attr1', 'virtual_attr2']
Overwriting as_json in your model should do the trick:
def as_json(options={})
{ :methods=>[:my_method] }.merge(options)
end

Rails: How can I render multiple objects to JSON?

I am trying to render multiple objects as JSON. This is my render call:
render :json => {:widget => #widget.to_json(:include => :foo),
:updated => Time.now.to_i}
I have to use to_json because of the include, and the addition updated so I know when the last call was made. The problem is that the to_json is rendered as a String instead of the object structure of the widget.
How do I get the full object structure of the widget and the updated information?
Move the :include => :foo into your Widget model.
class Widget < ActiveRecord::Base
def as_json(options = {})
super options.merge(:include => :foo)
end
end

Including nested objects in JSON response, from MongoMapper objects

class Api::StoresController < ApplicationController
respond_to :json
def index
#stores = Store.all(:include => :products)
respond_with #stores
end
end
Returns only stores without their products, as does
Store.find(:all).to_json(:include => :products)
The association is tested, I can see the nested products in console ouput from, say,
Store.first.products
What's the correct way to get them products included with MongoMapper?
Here are my models:
class Store
include MongoMapper::Document
many :products, :foreign_key => :store_ids
end
class Product
include MongoMapper::Document
key :store_ids, Array, :typecast => 'ObjectId'
many :stores, :in => :store_ids
end
UPDATE
In trying Scott's suggestion, I've added the following to the Store model:
def self.all_including_nested
stores = []
Store.all.each do |store|
stores << store.to_hash
end
end
def to_hash
keys = self.key_names
hash = {}
keys.each{|k| hash[k] = self[k]}
hash[:products] = self.products
hash[:services] = self.services
hash
end
And in the controller:
def index
#stores = Store.all_including_nested
respond_with #stores
end
Which looks like it should work? Assuming the array of hashes would have #to_json called on it, and then the same would happen to each hash and each Product + Service. I'm reading through ActiveSupport::JSON's source, and so far that's what I've grokked from it.
But, not working yet... :(
Have a look at the as_json() method. You put this in your models, define your json, and then simply call the render :json method and get what you want.
class Something
def as_json(options={})
{:account_name => self.account_name,
:expires_on => self.expires_on.to_s,
:collections => self.collections,
:type => "Institution"}
end
end
You'll notice self.collections which is a many relationship. That model also has as_json() defined:
class Collection
def as_json(options={})
{:name => self.name,
:title => self.title,
:isbn => self.isbn,
:publisher => self.publisher,
:monthly_views => self.monthly_views}
end
end
This one contains self.monthly_views which represents another many relationship.
Then in your controller:
#somethings = Something.all
render :json => #somethings
You might have to create your own method to generate a hash then turn the hash into JSON. I'm thinking something like this:
store = Store.first
keys = store.key_names
hash = {}
keys.each{|k| hash[k] = store[k]}
hash[:products] = store.products
hash.to_json

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