我创建了一个用户和一个位置模型（以及一个产品模型，但一次只有一个问题），当我在玩控制台时，我对一些结果感到惊讶。
模型
Class User < ActiveRecord::Base
# Before saving filters
before_save { self.email = email.downcase }
before_save :create_remember_token
# Validations
validates :name, presence: true,
length: { maximum: 50 }
VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
validates :email, presence: true,
format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
has_secure_password
validates :password, length: { minimum: 6 }
validates :password_confirmation, presence: true
# Associations
has_many :owned_products, class_name: "Product",
foreign_key: "owner_id",
dependent: :destroy
has_many :borrowed_products, class_name: "Product",
foreign_key: "borrower_id"
belongs_to :location
private
def create_remember_token
self.remember_token = SecureRandom.urlsafe_base64
end
end
Class Product < ActiveRecord::Base
validates :name, presence: true,
length: { maximum: 50 }
validates :owner, presence: true
belongs_to :owner, class_name: "User", foreign_key: "owner_id"
belongs_to :borrower, class_name: "User", foreign_key: "borrower_id"
belongs_to :location
end
Class Location < ActiveRecord::Base
has_many :users
has_many :products
end
迁移
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :name
t.string :email
t.string :password_digest
t.string :remember_token
t.integer :location_id
t.timestamps
end
add_index :users, :email, unique: true
add_index :users, :remember_token
add_index :users, :location_id
end
end
class CreateProducts < ActiveRecord::Migration
def change
create_table :products do |t|
t.string :name
t.integer :location_id
t.timestamps
end
add_index :products, :location_id
end
end
class CreateLocations < ActiveRecord::Migration
def change
create_table :locations do |t|
t.string :address
t.timestamps
end
end
end
位置属性是可访问的
class UsersController < ApplicationController
.
.
.
private
def user_params
params.require(:user).permit(:name, :email, :password, :password_confirmation, :location, :location_attributes)
end
end
然后我去我的控制台输入：
User.create(name: "Wahou", email: "wahou@bim.com", password: "motdepasse", password_confirmation: "motdepasse")
是什么让我：
(0.2ms) begin transaction
User Exists (0.4ms) SELECT 1 AS one FROM "users" WHERE LOWER("users"."email") = LOWER('wahou@bim.com') LIMIT 1
Binary data inserted for `string` type on column `password_digest` SQL (1.1ms) INSERT INTO "users" ("created_at", "email", "name", "password_digest", "remember_token", "updated_at") VALUES (?, ?, ?, ?, ?, ?) [["created_at", Fri, 24 May 2013 12:27:38 UTC +00:00], ["email", "wahou@bim.com"], ["name", "Wahou"], ["password_digest", "$2a$10$OhJ7SLA.vxO4N8IkZAXXQOibYQoX6G6E9/mGgmDpm8Hj48p8riDE."], ["remember_token", "-O72ULpG2tjrZSSi0BFB5A"], ["updated_at", Fri, 24 May 2013 12:27:38 UTC +00:00]]
(148.6ms) commit transaction
=> #<User id: 1, name: "Wahou", email: "wahou@bim.com", password_digest: "$2a$10$OhJ7SLA.vxO4N8IkZAXXQOibYQoX6G6E9/mGgmDpm8Hj...", remember_token: "-O72ULpG2tjrZSSi0BFB5A", admin: false, location_id: nil, created_at: "2013-05-24 12:27:38", updated_at: "2013-05-24 12:27:38">
然后我输入：
Location.create(address: "1, rue des prises de tête - Paris")
这给了我：
(0.2ms) begin transaction
SQL (6.0ms) INSERT INTO "locations" ("address", "created_at", "updated_at") VALUES (?, ?, ?) [["address", "1, rue des prises de tête - Paris"], ["created_at", Fri, 24 May 2013 12:27:22 UTC +00:00], ["updated_at", Fri, 24 May 2013 12:27:22 UTC +00:00]]
(121.6ms) commit transaction
=> #<Location id: 1, address: "1, rue des prises de tête - Paris", street: nil, city: nil, postal_code: nil, country: nil, longitude: nil, latitude: nil, created_at: "2013-05-24 12:27:22", updated_at: "2013-05-24 12:27:22">
所以，完全有信心，我这样做：
User.first.location = Location.first
这给了我：
User Load (0.5ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT 1
Location Load (0.4ms) SELECT "locations".* FROM "locations" ORDER BY "locations"."id" ASC LIMIT 1
=> #<Location id: 1, address: "1, rue des prises de tête - Paris", street: nil, city: nil, postal_code: nil, country: nil, longitude: nil, latitude: nil, created_at: "2013-05-24 12:27:22", updated_at: "2013-05-24 12:27:22">
当我输入User.first.location时，它会给我nil！
所以我想我忘记了某个地方。你有什么想法吗？
（如果您将产品替换为User，则完全相同......）
修改
我尝试仅键入User.first.location_id = 1，User.first.location始终为nil。
我找到定义用户位置的唯一方法是使用位置创建他，就像那样：Location.first.users.create(name: "Wahou", email: "wahou@bim.com", password: "motdepasse", password_confirmation: "motdepasse")。然后，它可以工作......但是当我想更新用户的位置时，我该怎么办？
编辑2
当我输入
u = User.first
我看到第一个用户被抓住了：
User Load (0.4ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT 1
=> #<User id: 2, name: "Numero1 Person", email: "numero1@person.com", password_digest: "$2a$10$sNwoTjOL4eqW.clxbM5FcuiE0AmPgzr8Kz0ewXgddAvP...", remember_token: "OQ2ZnLhPutwePTqn49r5PQ", admin: false, location_id: 2, created_at: "2013-05-29 07:59:13", updated_at: "2013-05-29 09:22:00">
然后我将Location.first影响到我的第一个用户的位置：
u.location = Location.first
我看到抓住了第一个位置：
Location Load (0.4ms) SELECT "locations".* FROM "locations" ORDER BY "locations"."id" ASC LIMIT 1
=> #<Location id: 1, address: "1, rue longue - 99999 LOIN - France", street: "1, rue longue", city: "LOIN", postal_code: 99999, country: "France", longitude: nil, latitude: nil, created_at: "2013-05-29 07:59:38", updated_at: "2013-05-29 07:59:38">
但是当我想保存它时......
u.save
......它不起作用！
(0.1ms) begin transaction
User Exists (0.4ms) SELECT 1 AS one FROM "users" WHERE (LOWER("users"."email") = LOWER('numero1@person.com') AND "users"."id" != 2) LIMIT 1
(0.2ms) rollback transaction
=> false
编辑3
如果我尝试输入以下代码......
User.first.update_attributes(location: Location.first)
它告诉我：
User Load (0.4ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT 1
Location Load (0.3ms) SELECT "locations".* FROM "locations" ORDER BY "locations"."id" ASC LIMIT 1
(0.1ms) begin transaction
User Exists (0.4ms) SELECT 1 AS one FROM "users" WHERE (LOWER("users"."email") = LOWER('numero1@person.com') AND "users"."id" != 2) LIMIT 1
(0.2ms) rollback transaction
=> false
解决
对我感到羞耻！我忘了在update_attributes中添加密码和password_confirmation。如果我这样做，它就有效！
这是正确的代码：
User.first.update_attributes(password: "password", password_confirmation: "password", location: Location.first)
答案 0 :(得分：1)
User.first.location_id = 1
将第一个用户加载到临时对象中，然后设置location_id，然后将其抛出而不保存。这就是为什么你的改变不持久。
@斯坦的
u= User.first
u.location = Location.first
u.save
将第一个用户加载到u，设置u的位置，然后保存以使其持久。之后
User.first.location
给出对象Location.first
另一种方式是用户update_attribut，它设置属性并保存更改，所以
User.first.update_attribute :location, Location.first
也有效并且使更改持久。
答案 1 :(得分：0)
u = User.first # => <User id: 1, name: "Wahou"....
l = Location.first #=> <Location id: 1, address: "1 rue.....
# set the location
u.location = l
#Save changes
u.save
#profit
User.first.location