encode_json

Returns a JSON string representing the model. Some configuration can be passed through options.

The option ActiveModel::Base.include_root_in_json controls the top-level behavior of to_json. It is true by default. When it is true, to_json will emit a single root node named after the object’s type. For example:

  konata = User.find(1)
  konata.to_json
  # => { "user": {"id": 1, "name": "Konata Izumi", "age": 16,
                  "created_at": "2006/08/01", "awesome": true} }

  ActiveRecord::Base.include_root_in_json = false
  konata.to_json
  # => {"id": 1, "name": "Konata Izumi", "age": 16,
        "created_at": "2006/08/01", "awesome": true}

The remainder of the examples in this section assume include_root_in_json is set to false.

Without any options, the returned JSON string will include all the model’s attributes. For example:

  konata = User.find(1)
  konata.to_json
  # => {"id": 1, "name": "Konata Izumi", "age": 16,
        "created_at": "2006/08/01", "awesome": true}

The :only and :except options can be used to limit the attributes included, and work similar to the attributes method. For example:

  konata.to_json(:only => [ :id, :name ])
  # => {"id": 1, "name": "Konata Izumi"}

  konata.to_json(:except => [ :id, :created_at, :age ])
  # => {"name": "Konata Izumi", "awesome": true}

To include any methods on the model, use :methods.

  konata.to_json(:methods => :permalink)
  # => {"id": 1, "name": "Konata Izumi", "age": 16,
        "created_at": "2006/08/01", "awesome": true,
        "permalink": "1-konata-izumi"}

To include associations, use :include.

  konata.to_json(:include => :posts)
  # => {"id": 1, "name": "Konata Izumi", "age": 16,
        "created_at": "2006/08/01", "awesome": true,
        "posts": [{"id": 1, "author_id": 1, "title": "Welcome to the weblog"},
                  {"id": 2, author_id: 1, "title": "So I was thinking"}]}

2nd level and higher order associations work as well:

  konata.to_json(:include => { :posts => {
                                 :include => { :comments => {
                                               :only => :body } },
                                 :only => :title } })
  # => {"id": 1, "name": "Konata Izumi", "age": 16,
        "created_at": "2006/08/01", "awesome": true,
        "posts": [{"comments": [{"body": "1st post!"}, {"body": "Second!"}],
                   "title": "Welcome to the weblog"},
                  {"comments": [{"body": "Don't think too hard"}],
                   "title": "So I was thinking"}]}