Ruby on Rails as json 将ActiveRecord结果转换为哈希数组

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 } }

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

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

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

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

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

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" } ] }

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" } ] }