Nested JSON in Rails

Question

First off, I would like to ask for your patience since this question is going to be really noobish. I've tried researching to no avail, as I can't put everything into place.

Anyway, I need to be able to render items in the database I will create as JSON. However, it is nested and I am unsure how would I go about creating the model for it:

{ "name": "name", "description": "description", "review": [ { "rating": "rating", "content": "content" }, { "rating": "rating", "content": "content" } ] }

Creating the Database

Do I create two tables first (i.e. Item and Review), like so?

rails g model Item name:string description:string review:string rails g model Review rating:string content:string

I've read that I need the accepts_nested_attributes_for method, but again, I am unsure how to use it.

class Item < ActiveRecord::Base has_many :reviews accepts_nested_attributes_for :reviews end class Review < ActiveRecord::Base belongs_to :item end

Populating the Database

If by some chance the above is correct, how do I actually populate the database using the console or seed.rb?

Rendering as JSON

This is what I have for non-nested entries:

def index @items = Items.all render :json => @items.as_json(:except => [:id, :created_at, :updated_at]) end

As you can tell, I am confused and lost. I would very much appreciate any input. Thank you.

Donovan · Accepted Answer · 2013-12-16 21:13:46Z

It looks like you're almost there, and are definitely on the right track.

When you create your models, you won't need review:string for Item, but you will need a item_id for Review (to hold the associated Item.id), like such:

rails g create Item name:string description:string rails g create Review rating:string content:string item_id:integer

The way rails associations work is it will store the item.id for the associated Item record in review.item_id. It will do this automagically, so all you need to do is use them.

To create the association between Review and Item:

new_review = Review.create(rating: 'great', content: 'Wonderfully done') new_item = Item.create(name: 'My Item', description: 'My Item description') new_item.reviews << new_review

To access the associated review(s) from Item:

new_item.reviews.each do |review| review.rating review.content end

Because it's a has_many relationship, an instance of Item will have a reviews method which returns an array of Review objects that have an item_id matching the current Item.id.

Likewise, an instance of Review will have a item method (note the singular use here), which just returns the single associated Item record object.

Make sense?

Additionally, when you output a record with an association in JSON (as you've done in your example), it should create output close to what your example shows.

Render your JSON as follows:

@items = Item.all render :json => @items.to_json(:include => [:reviews], :except => [:id, :created_at, :updated_at])

Thank you for your response. I got stuck at storing the newly-made review, unfortunately. It tells me it cannot find the method--undefined method 'reviews'.
Make sure you've created the associations like in your example and applied the database migration with rake db:migrate.
Item.reviews << new_review is incorrect. You need to associate data with an instance of Item, not on the Item class itself.

Collectives™ on Stack Overflow

Nested JSON in Rails

1 Answer 1

6 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Related