Rails Generate Nested JSON

Question

I have two objects, an @article and a @profile. Article is a model and @profile is a Struct. I'd like to end up with some JSON that looks like this:

{
    "article": {
        "title": "this is a title",
        "author": "Author McAuthor",
        "profile": {
            "first_name": "Bobby",
            "last_name": "Fisher"
        }
    }
}

As of now, I can just manually create this by doing something like:

@json = { article: { title: @article.title, author: @article.author, profile: { first_name: @profile.first_name, last_name: @profile.last_name } }}

I feel like building the json object this way is sorta crude, also, every time I change the author model, I might have to change this code. It would be great if I could find an easier way to build these json objects without having to do so manually... Any help? Thanks!

Build whatever ruby structure you like (consisting of arrays and hashes), and then use .to_json on it. But then, I just found at least one person does not like that - blog.gomiso.com/2011/05/16/… — Mörre
– Mörre, Commented Feb 11, 2013 at 23:33
If you have a Ruby variable, a has for example, you can call variable.to_json and get the json string as a result. Rails adds a to_josn method on Object (all it does is call ActiveSupport::JSON.encode(self, options)). See api.rubyonrails.org, enter to_json in the search box. — Mörre
– Mörre, Commented Feb 11, 2013 at 23:40
i am aware of those methods. i am trying to nest one object inside another object in json without building the strings manually, then add new attributes to where i'm building the json string every time the objects update. — botbot
– botbot, Commented Feb 11, 2013 at 23:43
It's better to override as_json: jonathanjulian.com/2010/04/rails-to_json-or-as_json — Chris Salzberg
– Chris Salzberg, Commented Feb 11, 2013 at 23:43

Sean Hill · Accepted Answer · 2013-02-12 00:03:28Z

2

In addition to shioyama's correct answer, you can use rabl to craft your JSON objects, similar to how ERB works for views.

For example, you would create a 'view', say, index.rabl. It would look like:

collection @articles
attributes :author, :title
child(:profile) { attributes :first_name, :last_name }

answered Feb 12, 2013 at 0:03

Sean Hill

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3 Comments

Mark Thomas Over a year ago

+1 This is what I was going to say. The rabl gem builds your JSON API using a standard Rails view. This gives you the ultimate flexibility and avoids the tendency to couple your model schema to your API.

botbot Over a year ago

@Sean Hill curious, if i wanted to create that child(:profile) but then create a custom attribute called "profile_views" how would i do that?

Sean Hill Over a year ago

Then you would do child(:profile) { attributes :first_name, :last_name; node(:profile_views) { |profile| profile.profile_views } }, assuming that profile_views is a method on the profile instance.

Community · Accepted Answer · 2017-05-23 11:48:51Z

2

Rails serializes objects in two steps, first by calling as_json to create the object to be serialized, then by calling to_json to actually create the JSON string.

Generally, if you want to customize how your models are represented in JSON, it's best to override as_json. Assuming your profile struct is a virtual attribute (i.e. defined with attr_accessor, not saved in the db), you could do this in your Article model:

def as_json(options = {})
  super((options || {}).merge({
    :methods => :profile
  }))
end

Hope that helps. See also:

edited May 23, 2017 at 11:48

CommunityBot

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answered Feb 11, 2013 at 23:49

Chris Salzberg

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4 Comments

Chris Salzberg Over a year ago

Updated my answer to pass through any options to super.

botbot Over a year ago

+1 thanks @shioyama. i will look into that. \@profile is not a virtual attribute, but perhaps it should be?

botbot Over a year ago

so this code is saying that we are going to merge the result of the method profile into the article json?

Chris Salzberg Over a year ago

It says we are going to merge the key/value pair :methods => :profile into whatever options are passed in to as_json when it is caled. The :methods option is used to declare any method return values you want to include in your JSON. So if you have a method profile which returns an object, then it will be included and converted to JSON using to_json. Hope that makes sense.

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