Rails STI 和 has_many 通过关联不起作用，SQLException：没有这样 table

Question

我有以下型号：

class Test < ApplicationRecord
end

class Exam < Test
end

class Practice < Test
  has_many :relations
  has_many :questions, through: :relations
end

class Relation < ApplicationRecord
  belongs_to :practice
  belongs_to :question
end

class Question < ApplicationRecord
  has_many :relations
  has_many :practices, through: :relations
end

这是我的架构：

 create_table "questions", force: :cascade do |t|
    t.string "title"
    t.text "text"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "relations", force: :cascade do |t|
    t.integer "practice_id"
    t.integer "question_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["practice_id"], name: "index_relations_on_practice_id"
    t.index ["question_id"], name: "index_relations_on_question_id"
  end

  create_table "tests", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

当我在 rails 控制台中尝试时：

@p = Practice.new
@p.save
@q = Question.new 
@q.save

Practice.last.questions << Question.last

我收到这个错误：

Question Load (0.2ms)  SELECT  "questions".* FROM "questions" ORDER BY "questions"."id" DESC LIMIT ?  [["LIMIT", 1]]
   (0.1ms)  begin transaction
  SQL (0.4ms)  INSERT INTO "relations" ("practice_id", "question_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["practice_id", 2], ["question_id", 1], ["created_at", "2017-10-26 06:09:42.581082"], ["updated_at", "2017-10-26 06:09:42.581082"]]
   (0.1ms)  rollback transaction
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such table: main.practices: INSERT INTO "relations" ("practice_id", "question_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)

错误很明显，它没有找到 table practices 但我该如何解决这个问题？我不明白如何指定使用 table 测试，而不是实践。感谢任何帮助

Answer 1

应该没有 practices table 因为 Practice 继承了 Test 并且您想使用 STI 模式。我已经在我的机器上重复了您的模型和模式，它按预期工作。所以要么你对 SQLite 或 spring.

有一些问题

用 spring stop 冷静下来 spring 然后尝试用 rails db:reset 重新创建数据库并确保没有错误。

此外，我希望这只是示例代码，在现实生活中你不会将 sql 关系命名为 relations =)

Rails STI 和 has_many 通过关联不起作用，SQLException：没有这样 table

Rails STI and has_many through association not working, SQLException: no such table

ruby

ruby-on-rails

associations

single-table-inheritance

has-many-through