如果模型有一个包含 ID 的集合，Rails 会获取 ID 数组

Question

High level what I'm trying to do. I have a House model and a House has_many Rooms . Both House and Room have an id property. I'm trying to get an array of House ids that contain a rooms with a certain id: data: (rails 4.2.6)

houses = [{
  id: 1,
  rooms: [{ id: 1}, {id: 2}, {id: 3}]
},{
  id: 2,
  rooms: [{id: 2}]
}]

pseudocode

House.where(rooms: contain(id: 2))

this should return [1,2] because both houses have room id of 2

House.where(rooms: contain(id: 1))

this should return [1].

Answer 1

如果您只关心id值，您可以使用pluck ：

House.where(...).pluck(:id)

Answer 2

尝试这个：

House.joins(:rooms).where(:rooms => {:id => 5}).pluck(:id)