Active Model JSON Serializer¶ ↑

返回一个表示模型的哈希。可以通过 options 传递一些配置。

include_root_in_json 选项控制 as_json 的顶层行为。如果设置为 true，as_json 将会输出一个以对象类型命名的单一根节点。include_root_in_json 选项的默认值为 false。

user = User.find(1)
user.as_json
# => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#     "created_at" => "2006-08-01T17:27:133.000Z", "awesome" => true}

ActiveRecord::Base.include_root_in_json = true

user.as_json
# => { "user" => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#                  "created_at" => "2006-08-01T17:27:13.000Z", "awesome" => true } }

通过设置 :root 选项为 true 也可以实现此行为，例如：

user = User.find(1)
user.as_json(root: true)
# => { "user" => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#                  "created_at" => "2006-08-01T17:27:13.000Z", "awesome" => true } }

如果愿意，:root 也可以设置为一个自定义字符串键，例如：

user = User.find(1)
user.as_json(root: "author")
# => { "author" => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#                  "created_at" => "2006-08-01T17:27:13.000Z", "awesome" => true } }

在没有任何 options 的情况下，返回的 Hash 将包含模型的所有属性。

user = User.find(1)
user.as_json
# => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#      "created_at" => "2006-08-01T17:27:13.000Z", "awesome" => true}

:only 和 :except 选项可用于限制包含的属性，其工作方式类似于 attributes 方法。

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

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

要包含模型上某些方法调用的结果，请使用 :methods

user.as_json(methods: :permalink)
# => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#      "created_at" => "2006-08-01T17:27:13.000Z", "awesome" => true,
#      "permalink" => "1-konata-izumi" }

要包含关联，请使用 :include

user.as_json(include: :posts)
# => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#      "created_at" => "2006-08-01T17:27:13.000Z", "awesome" => true,
#      "posts" => [ { "id" => 1, "author_id" => 1, "title" => "Welcome to the weblog" },
#                   { "id" => 2, "author_id" => 1, "title" => "So I was thinking" } ] }

第二层及更高阶的关联也同样适用

user.as_json(include: { posts: {
                           include: { comments: {
                                          only: :body } },
                           only: :title } })
# => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#      "created_at" => "2006-08-01T17:27:13.000Z", "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" } ] }

从 JSON 字符串设置模型的 attributes。返回 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

include_root 的默认值为 false。如果给定的 JSON 字符串包含一个单一的根节点，您可以将其更改为 true。

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