具有 2 个父级别的 activerecord 模型

Question

一个用户可以有很多问题。许多用户可以参与一个问题并为同一个问题提供多个答案。用户和问题之间的关系似乎运行良好。问题在于答案。

model/user.rb

  has_and_belongs_to_many :questions
  has_many :answers

model/question.rb

  has_and_belongs_to_many :users
  has_many :answers

model/answer.rb

  has_one :question
  has_one :user, :through => :question

这是我在控制台中尝试的：

irb(main):022:0> u1.questions.first.answers.create(answer: "foo1", order:1)
   (0.2ms)  BEGIN
  Answer Exists (0.5ms)  SELECT  1 AS one FROM "answers" WHERE "answers"."answer" = $1 LIMIT $2  [["answer", "foo1"], ["LIMIT", 1]]
  SQL (0.4ms)  INSERT INTO "answers" ("created_at", "updated_at", "answer", "order", "question_id") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["created_at", 2017-03-31 19:31:04 UTC], ["updated_at", 2017-03-31 19:31:04 UTC], ["answer", "foo1"], ["order", 1], ["question_id", 1]]
   (13.5ms)  COMMIT
=> #<Answer id: 6, created_at: "2017-03-31 19:31:04", updated_at: "2017-03-31 19:31:04", answer: "foo1", order: 1, user_id: nil, question_id: 1>
irb(main):023:0> u1.questions.first.answers.create(answer: "bar1", order:2)
   (0.4ms)  BEGIN
  Answer Exists (0.9ms)  SELECT  1 AS one FROM "answers" WHERE "answers"."answer" = $1 LIMIT $2  [["answer", "bar1"], ["LIMIT", 1]]
  SQL (0.5ms)  INSERT INTO "answers" ("created_at", "updated_at", "answer", "order", "question_id") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["created_at", 2017-03-31 19:31:04 UTC], ["updated_at", 2017-03-31 19:31:04 UTC], ["answer", "bar1"], ["order", 2], ["question_id", 1]]
   (19.9ms)  COMMIT
=> #<Answer id: 7, created_at: "2017-03-31 19:31:04", updated_at: "2017-03-31 19:31:04", answer: "bar1", order: 2, user_id: nil, question_id: 1>
irb(main):024:0> u2.questions.first.answers.create(answer: "foo2", order:1)
   (0.7ms)  BEGIN
  Answer Exists (0.6ms)  SELECT  1 AS one FROM "answers" WHERE "answers"."answer" = $1 LIMIT $2  [["answer", "foo2"], ["LIMIT", 1]]
  SQL (0.9ms)  INSERT INTO "answers" ("created_at", "updated_at", "answer", "order", "question_id") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["created_at", 2017-03-31 19:31:04 UTC], ["updated_at", 2017-03-31 19:31:04 UTC], ["answer", "foo2"], ["order", 1], ["question_id", 1]]
   (16.7ms)  COMMIT
=> #<Answer id: 8, created_at: "2017-03-31 19:31:04", updated_at: "2017-03-31 19:31:04", answer: "foo2", order: 1, user_id: nil, question_id: 1>
irb(main):025:0> u2.questions.first.answers.create(answer: "bar2", order:2)
   (0.5ms)  BEGIN
  Answer Exists (0.6ms)  SELECT  1 AS one FROM "answers" WHERE "answers"."answer" = $1 LIMIT $2  [["answer", "bar2"], ["LIMIT", 1]]
  SQL (0.5ms)  INSERT INTO "answers" ("created_at", "updated_at", "answer", "order", "question_id") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["created_at", 2017-03-31 19:31:05 UTC], ["updated_at", 2017-03-31 19:31:05 UTC], ["answer", "bar2"], ["order", 2], ["question_id", 1]]
   (14.9ms)  COMMIT
=> #<Answer id: 9, created_at: "2017-03-31 19:31:05", updated_at: "2017-03-31 19:31:05", answer: "bar2", order: 2, user_id: nil, question_id: 1>

鉴于 user_id 为空，除非我指定，否则很明显有些地方是错误的。鉴于我是通过问题从用户对象创建的，我希望 user_id 已填充。

irb(main):027:0* u1.questions.first.answers.count
   (0.7ms)  SELECT COUNT(*) FROM "answers" WHERE "answers"."question_id" = $1  [["question_id", 1]]
=> 4

正如我在这里看到的，它只是按 question_id 过滤。我希望从 question_id 和 user_id 中检索答案

这个问题可以解决吗？我应该换一种方式吗？

谢谢

更新

总而言之，这是我想要实现的目标：

User.first.answers.where(question_id: 1)

查询的样子：

SELECT "answers".* FROM "answers" WHERE "answers"."user_id" = $1 AND "answers"."question_id" = $2  [["user_id", 1], ["question_id", 1]]

我希望能够做到：

User.first.questions.first.answers

并获得 user_id 和 question_id 的答案

谢谢

Answer 1

我认为您应该使用belongs_to 来代替:user 和:question（而不是has_one），并手动将用户设置为来自控制器中current_user 的答案。