to_json
to_json(options = {})Returns a JSON string representing the model. Some configuration is available through options.
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"}]}
2Notes
Multiple associations on the same level
You can also specify multiple associations that are on the same level, like this:
konata = User.find(1)
konata.to_json(:include => [:posts, :roles])
{"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"}], "roles": [{"id":1, "user_id":1, "name": "Admin"}, {"id":2, "user_id":1, "name": "Moderator"}]}
Including instance methods to JSON output
Use :methods parameter to include ActiveRecord instance methods to JSON output. :only and :except uses DB columns only.
@events.to_json(:include => {
:images => {
:only => [], :methods => [:public_url] }})
In the previous example events have multiple images and only public_url instance method is included in the JSON output.