（Rails 5.1）自联接关联给出错误：没有这样的表

Question

FIXED

It works in 5.0.6

The problem is within your generator.

rails g model Employees manager:references

Produces the wrong migration. Read on if you want the fix.

I have a problem with self-join associations...

class Employee < ApplicationRecord
    has_many :subordinates, class_name: "Employee", foreign_key: "manager_id"

    belongs_to :manager, class_name: "Employee", optional: true
end

When trying to create a "Employee" record, gives error "No such table main.managers" (at the bottom):

>> Employee.create(name: "Matt")
   (0.4ms)  begin transaction
  SQL (1.5ms)  INSERT INTO "employees" ("name", "created_at", "updated_at") VALUES (?, ?, ?)  [["name", "Matt"], ["created_at", "2018-02-19 16:38:21.835022"], ["updated_at", "2018-02-19 16:38:21.835022"]]
   (0.2ms)  rollback transaction
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such table: main.managers: INSERT INTO "employees" ("name", "created_at", "updated_at") VALUES (?, ?, ?)

The code is taken out from the RoR guide. How do I correct it?

I emphasize that it is a self-join table. Therefore there is no "Manager" model or "managers" table.

Rails version 5.1.5

Solution:

It's because of the migration. Using the command

rails g model Employee name:string manager:references

Produces different code in 5.0.6 . You cannot have such a migration:

create_table :employees do |t|
  t.string :name
  t.references :manager, foreign_key: true #mistake

  t.timestamps
end

Change it to:

t.references :manager, index: true

RoR self-join guide I'm referring to

Answer 1

如果员工为belongs_to manager，那么您应该拥有类似Manager.employee.create的内容

Answer 2

在belongs_to关联上也设置foreign_key属性。