Rails：过滤范围内的嵌套属性

Question

我的模型有以下关系：

Building 有很多 Rooms 有很多 Beds 有很多 Accommodations，

我想渲染所有Buildings，但在日期范围内创建Accommodations。从其他答案中，我了解到我需要为 Building 模型创建范围，但我不明白如何在此范围内过滤此类嵌套属性。

编辑：

假设我有Building 1、2 和 3。每个Building 都有自己的Rooms，Beds 有Accommodations。假设只有Building 1 有一个Accommodation 在范围内。所以返回的数据一定是：

Building 1
    ...
    Room n
      ...
        Bed n
         Accommodation that is in range
        Bed n+1
      ...
    ...
Building 2 (accommodation arrays in beds are empty since there are no accommodations that are in range)
    ...
Building 3 (accommodation arrays is beds are empty since there are no accommodations that are in range)
    ...

Answer 1

为了避免在模型中编写过度嵌套的连接查询setup indirect relations：

class Building
  has_many :rooms
  has_many :beds, though: :rooms
  has_many :accommodations, through: :beds
end

class Room
  belongs_to :building
  has_many :beds
  has_many :accommodations, through: :beds
end

class Bed
  belongs_to :room
  has_many :accommodations
  has_one :building, through: :room
end

class Accommodation
  belongs_to :bed
  has_one :room, through: :bed
  has_one :building, through: :room
end  

这将让您直接查询building.accommodations，ActiveRecord 将为您加入中间表。

然后在查询时使用Range：

Building.includes(:accommodations)
        .where(accommodations: { created_at: start_time..end_time })

这将使用大多数数据库驱动程序构造一个WHERE 'accommodations.created_at' BETWEEN ...。

难题的另一个关键部分是您没有过滤嵌套属性。相反，上面发生的是您使用的是join and setting conditions on the joined table。

Answer 2

class Building
  scope :accomodations_for_dates, lambda { |start_date, end_date|
    joins(rooms: [beds: :accomodations]).where("accomodations.created_at >= #{start_date} AND accomodations.end_date <= #{end_date}")
  }
end

对于 PostgreSQL 和 MySQL 数据库，您可以使用BETWEEN：

"accomodations.created_at BETWEEN #{start_date} AND #{end_date}"

要返回所有建筑物，但要使用过滤后的住宿，包括：

includes(rooms: [beds: :accomodations]).where(accomodations: { created_at: start_date..end_date })