如何通过Ruby中的联接表进行单个查询以检索与模型相关的对象

Question

我有以下相关模型：

Country 
  has_many :states

State 
  belongs_to :country
  has_many :counties

County 
  belongs_to :State
  has_many :municipalities
  has_many :cities, through: :municipalities

City
  has_many :municipalities
  has_many :counties, through: :municipalities 

Municipality
  belongs_to :county
  belongs_to :city

我希望能够调用类似@ country.cities之类的东西，并使其通过其相关对象返回属于一个国家的所有城市。 任何反馈表示赞赏，谢谢！

Answer 1

尝试：

Country
  has_many :states
  has_many :cities, through: :states

State
  has_many :counties
  has_many :cities, through: :counties

Answer 2

干得好：

Country 
  has_many :states
  has_many :counties      , through: :states
  has_many :municipalities, through: :counties
  has_many :cities        , through: :municipalities