module ActiveModel::Serializers::JSON - activemodel-4.2.4 Documentation

# module ActiveModel::Serializers::JSON

## Active Model JSON Serializer¶ ↑

### Public Instance Methods

as_json(options = nil) click to toggle source

Returns a hash representing the model. Some configuration can be passed through `options`.

The option `include_root_in_json` controls the top-level behavior of `as_json`. If `true`, `as_json` will emit a single root node named after the object's type. The default value for `include_root_in_json` option is `false`.

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

    ActiveRecord::Base.include_root_in_json = true

    user.as_json
    # => { "user" => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
    #                  "created_at" => "2006/08/01", "awesome" => true } }

This behavior can also be achieved by setting the `:root` option to `true` as in:

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

Without any `options`, the returned Hash will include all the model's attributes.

    user = User.find(1)
    user.as_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.

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

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

To include the result of some method calls on the model use `:methods`:

    user.as_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`:

    user.as_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" } ] }

Second level and higher order associations work as well:

    user.as_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" } ] }

    # File lib/active_model/serializers/json.rb, line 88
    def as_json(options = nil)
      root = if options && options.key?(:root)
        options[:root]
      else
        include_root_in_json
      end

      if root
        root = model_name.element if root == true
        { root => serializable_hash(options) }
      else
        serializable_hash(options)
      end
    end

from_json(json, include_root=include_root_in_json) click to toggle source

Sets the model `attributes` from a JSON string. Returns `self`.

    class Person
      include ActiveModel::Serializers::JSON

      attr_accessor :name, :age, :awesome

      def attributes=(hash)
        hash.each do |key, value|
          send("#{key}=", value)
        end
      end

      def attributes
        instance_values
      end
    end

    json = { name: 'bob', age: 22, awesome:true }.to_json
    person = Person.new
    person.from_json(json) # => #<Person:0x007fec5e7a0088 @age=22, @awesome=true, @name="bob">
    person.name            # => "bob"
    person.age             # => 22
    person.awesome         # => true

The default value for `include_root` is `false`. You can change it to `true` if the given JSON string includes a single root node.

    json = { person: { name: 'bob', age: 22, awesome:true } }.to_json
    person = Person.new
    person.from_json(json, true) # => #<Person:0x007fec5e7a0088 @age=22, @awesome=true, @name="bob">
    person.name                  # => "bob"
    person.age                   # => 22
    person.awesome               # => true

    # File lib/active_model/serializers/json.rb, line 137
    def from_json(json, include_root=include_root_in_json)
      hash = ActiveSupport::JSON.decode(json)
      hash = hash.values.first if include_root
      self.attributes = hash
      self
    end