我只是尝试使用Rails 5，并且遇到了 accepts_nested_attributes_for 。但我无法让它发挥作用。 我做错了什么？
以下是我的模特：
以下是SQL表定义
型号代码
class Person < ApplicationRecord
has_many :activities
accepts_nested_attributes_for :activities
end
class Activity < ApplicationRecord
belongs_to :person
end
阅读API文档（accepts_nested_attributes_for）
我创建了一个params哈希，并尝试将其提交给Person Class。
params = {person: {name: 'Joe', activities_attributes: [{description: "Hiking"}]} }
当我尝试运行此特定代码时，不是创建名为＆＃34; Joe＆＃34;的新人员记录，而是在＆＃34;徒步旅行＆＃34;的活动下创建新的关联记录，而不是简单的失败。 / p>
>> params = {person: {name: 'Joe', activities_attributes: [{description: "Hiking"}]} }
{:person=>{:name=>"Joe", :activities_attributes=>[{:description=>"Hiking"}]}}
>> Person.create(params[:person])
(12.6ms) BEGIN
(0.6ms) ROLLBACK
#<Person id: nil, name: "Joe", age: nil, adult: nil, created_at: nil, updated_at: nil>
但一次只做一步似乎工作正常：
>> Person.create(:name => "Joe")
(6.3ms) BEGIN
SQL (31.6ms) INSERT INTO "people" ("name", "created_at", "updated_at") VALUES ($1, $2, $3) RETURNING "id" [["name", "Joe"], ["created_at", 2016-07-13 19:30:35 UTC], ["updated_at", 2016-07-13 19:30:35 UTC]]
>> a = Person.first
Person Load (9.1ms) SELECT "people".* FROM "people" ORDER BY "people"."id" ASC LIMIT $1 [["LIMIT", 1]]
#<Person id: 35, name: "Joe", age: nil, adult: nil, created_at: "2016-07-13 19:30:35", updated_at: "2016-07-13 19:30:35">
>> a.activities_attributes = [{:name => "Hiking"}]
[{:name=>"Hiking"}]
>> a.save
(0.2ms) BEGIN
Person Load (0.6ms) SELECT "people".* FROM "people" WHERE "people"."id" = $1 LIMIT $2 [["id", 35], ["LIMIT", 1]]
SQL (13.0ms) INSERT INTO "activities" ("person_id", "name", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["person_id", 35], ["name", "Hiking"], ["created_at", 2016-07-13 19:31:02 UTC], ["updated_at", 2016-07-13 19:31:02 UTC]]
(6.8ms) COMMIT
true
>> a
#<Person id: 35, name: "Joe", age: nil, adult: nil, created_at: "2016-07-13 19:30:35", updated_at: "2016-07-13 19:30:35">
>> a.activities
Activity Load (12.4ms) SELECT "activities".* FROM "activities" WHERE "activities"."person_id" = $1 [["person_id", 35]]
#<ActiveRecord::Associations::CollectionProxy [#<Activity id: 7, person_id: 35, name: "Hiking", created_at: "2016-07-13 19:31:02", updated_at: "2016-07-13 19:31:02", description: nil>]>
人员表
testing_development=# \d+ people;
Table "public.people"
Column | Type | Modifiers | Storage | Stats target | Description
------------+-----------------------------+-----------------------------------------------------+----------+--------------+-------------
id | integer | not null default nextval('people_id_seq'::regclass) | plain | |
name | character varying | | extended | |
age | integer | | plain | |
adult | boolean | | plain | |
created_at | timestamp without time zone | not null | plain | |
updated_at | timestamp without time zone | not null | plain | |
Indexes:
"people_pkey" PRIMARY KEY, btree (id)
活动表
testing_development=# \d+ activities;
Table "public.activities"
Column | Type | Modifiers | Storage | Stats target | Description
-------------+-----------------------------+---------------------------------------------------------+----------+--------------+-------------
id | integer | not null default nextval('activities_id_seq'::regclass) | plain | |
person_id | integer | | plain | |
name | text | | extended | |
created_at | timestamp without time zone | not null | plain | |
updated_at | timestamp without time zone | not null | plain | |
description | text | | extended | |
Indexes:
"activities_pkey" PRIMARY KEY, btree (id)
"index_activities_on_person_id" btree (person_id)
答案 0 :(得分：1)
我得到了它的工作，但不确定这是Rails 5的错误，还是只是改变了事情的方式。
我是如何工作的，看看这个问题是否被隔离到rails 5.我创建了一个Rails 4.2应用程序，具有相同的确切代码，它工作。
一旦我开始工作，我就在网上看了一下这些帖子，看看我是否能找到为什么会出现这种情况。这些是帮助我的资源：
Trouble with accepts_nested_attributes_for in Rails 5.0.0.beta3, -api option
class Post < ApplicationRecord
belongs_to :member, optional: true
end
我添加了这一行，它就像一个魅力。
>> params = {person: {name: "Testing", activities_attributes: [{name: "Testing"}]}}
{:person=>{:name=>"Testing", :activities_attributes=>[{:name=>"Testing"}]}}
>> Person.create(params[:person])
(0.1ms) BEGIN
SQL (6.5ms) INSERT INTO "people" ("name", "created_at", "updated_at") VALUES ($1, $2, $3) RETURNING "id" [["name", "Testing"], ["created_at", 2016-07-13 21:30:45 UTC], ["updated_at", 2016-07-13 21:30:45 UTC]]
SQL (12.5ms) INSERT INTO "activities" ("person_id", "name", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["person_id", 37], ["name", "Testing"], ["created_at", 2016-07-13 21:30:45 UTC], ["updated_at", 2016-07-13 21:30:45 UTC]]
(2.9ms) COMMIT
#<Person id: 37, name: "Testing", age: nil, adult: nil, created_at: "2016-07-13 21:30:45", updated_at: "2016-07-13 21:30:45">
此页面显示Rails 5中发生了哪些更改，以便发生此行为。
http://blog.bigbinary.com/2016/02/15/rails-5-makes-belong-to-association-required-by-default.html
答案 1 :(得分：0)
使用optional: true并非真正正确的解决方案 - 它是一种解决方法。在5.1.1之前的Rails 5版本中，accepts_nested_attributes_for中存在一个错误。请参阅https://github.com/rails/rails/issues/25198和Trouble with accepts_nested_attributes_for in Rails 5.0.0.beta3, -api option。
解决方案是使用inverse_of:选项，或者更好的是升级到Rails 5.1.1。