Question

我有以下设置：

class Invite < ActiveRecord::Base
    belongs_to :attending_guest, :class_name => "User", :foreign_key => :attending_guest_id
    belongs_to :attending_event, :class_name => "Event"
end

class Event < ActiveRecord::Base
    belongs_to :creator, :class_name => "User"
    has_many :invites
    has_many :attendees, :through => :invites, :source => :attending_event
end

class User < ActiveRecord::Base
    has_many :created_events, :foreign_key => "creator_id", :class_name => "Event"
    has_many :invites
    has_many :attended_events, through: :invites, source: :attending_guest
end

以下架构：

ActiveRecord::Schema.define(version: 20151114095321) do

  create_table "events", force: :cascade do |t|
    t.string   "title"
    t.string   "date"
    t.text     "description"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
    t.integer  "creator_id"
    t.string   "location"
  end

  add_index "events", ["creator_id"], name: "index_events_on_creator_id"

  create_table "invites", force: :cascade do |t|
    t.datetime "created_at",         null: false
    t.datetime "updated_at",         null: false
    t.integer  "attending_guest_id"
    t.integer  "attending_event_id"
  end

  add_index "invites", ["attending_event_id"], name: "index_invites_on_attending_event_id"
  add_index "invites", ["attending_guest_id"], name: "index_invites_on_attending_guest_id"

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

end

创建此关系后，在cnosole中，运行时出现以下错误：

2.2.0 :001 > u = User.first
  User Load (0.2ms)  SELECT  "users".* FROM "users"  ORDER BY "users"."id" ASC LIMIT 1
 => #<User id: 1, name: "User One", email: "user@example.com", created_at: "2015-11-14 09:20:26", updated_at: "2015-11-14 09:20:26"> 
2.2.0 :002 > u.attended_events
  User Load (0.4ms)  SELECT "users".* FROM "users" INNER JOIN "invites" ON "users"."id" = "invites"."attending_guest_id" WHERE "invites"."user_id" = ?  [[nil, 1]]
SQLite3::SQLException: no such column: invites.user_id: SELECT "users".* FROM "users" INNER JOIN "invites" ON "users"."id" = "invites"."attending_guest_id" WHERE "invites"."user_id" = ?
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: invites.user_id: SELECT "users".* FROM "users" INNER JOIN "invites" ON "users"."id" = "invites"."attending_guest_id" WHERE "invites"."user_id" = ?

有谁可以解释发生了什么？我尝试了很多不同的东西但是无法理解问题是什么......任何帮助都会非常感激！非常感谢！

Answer 1

此错误表明您在user_id中没有invites列。

按照惯例，Rails假定用于在另一个模型上保存外键的列是此模型的名称，并添加了后缀_id。：foreign_key选项允许您直接设置外键的名称

所以你可以补充一下：

class User < ActiveRecord::Base
  has_many :invites, :foreign_key => :attending_guest_id
end

Rails关联：SQLite3 :: SQLException：没有这样的列

1 个答案: