Question

我有以下内容：

class ObjectA < ActiveRecord::Base
  has_one   :object_b
end

class ObjectB < ActiveRecord::Base
  belongs_to   :object_a
  has_one   :object_c
end

class ObjectC < ActiveRecord::Base
  belongs_to   :object_b
end

因此，做ObjectA.eager_load（：object_b）会显着地加载ObjectB。但是我每次打电话时都试图加载整个层次结构，而不必发出新的查询：object_a.object_b.object_c

想法？

Answer 1

如果您执行类似

的操作

ObjectA.includes(object_b: :object_c).where(...)

对于符合ObjectA条件的每个ObjectB，这会急切加载ObjectC个相关ObjectA和嵌套where(...)。

如果您希望在需要执行热切加载时避免重复上述查询格式，可以在ObjectA上创建一个类方法。

class ObjectA < ActiveRecord::Base
  has_one   :object_b

  def self.with_related(conditions)
    includes(object_b: :object_c).where(conditions)
  end
end

参考： Eager Loading of Associations

Rails 4急切地在模型中加载模型

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