rails 中链方法的别名

Question

我有一个用户自加入关联。 这是我目前的数据

Click to view data table

我的用户模型
User.rb

class User < ApplicationRecord
  belongs_to :mother, class_name: "User", optional: true
  belongs_to :father, class_name: "User", optional: true
end

我可以在 Rails 控制台中执行以下操作。

irb(main):001:0> user = User.find(1)
   (0.4ms)  SELECT sqlite_version(*)
  User Load (0.3ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 1], ["LIMIT", 1]]
=> #<User id: 1, name: "rj", mother_id: 3, father_id: 2>

irb(main):002:0> user.father
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 2], ["LIMIT", 1]]
=> #<User id: 2, name: "father", mother_id: 4, father_id: 5>

irb(main):003:0> user.father.father
  User Load (0.1ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 5], ["LIMIT", 1]]
=> #<User id: 5, name: "grandfather", mother_id: nil, father_id: nil>

简而言之，如果我做user.father.father或user.father.mother，我可以得到rj的父亲的父亲（祖父）和rj的父亲的母亲（祖母）的对象

有没有办法让我创建一个别名，例如 user.grandfather 和 user.grandmother 以获得相同的结果？

Answer 1

在 User.rb 模型中，添加以下方法

def paternal_grandfather
   father&.father
end

def paternal_grandmother
  father&.mother
end

def maternal_grandfather
   mother&.father
end

def maternal_grandmother
  mother&.mother
end

或者，在组合形式中，我们可以将方法用作

def grandfather
  father&.father || mother&.father
end

def grandmother
  father&.mother || mother&.mother
end

将其用作user.grandfather 和user.grandmother

Answer 2

class User < ApplicationRecord
  belongs_to :mother, class_name: "User", optional: true
  belongs_to :father, class_name: "User", optional: true
  has_one :grandfather, through: :father, source: :father
  has_one :grandmother, through: :father, source: :mother
end