Question

如何根据连接模型属性查找对象？鉴于以下内容：

class Book < ActiveRecord::Base
  has_many :libraries
  has_many :renters, :through => :libraries
end

class Renter < ActiveRecord::Base
  has_many :libraries
  has_many :books, :through => :libraries
end

class Library < ActiveRecord::Base
  belongs_to :renter
  belongs_to :book

  # model has a location:integer property
end

我如何使用以下伪代码进行搜索：

locations = [1,2]
@all_books = Book.where(:location => locations)

Answer 1

您需要加入这两个表。尝试：

locations = [1,2]
@all_books = Book.joins(:libraries).where(libraries: { :location => locations })

这会加入books和libraries，并使用libraries.location in(1,2)条件过滤记录。

Answer 2

locations = [1,2]
@all_books = Book.joins(:libraries).where("libraries.location in (?)", locations).uniq

我正在使用uniq，因为当您加入has_many关系时，您将获得同一本书的多条记录

Rails基于连接模型属性获取对象

2 个答案: