ruby-on-rails - has_many :through and fields_for 问题

Question

我有一个非常基本的联想:

# user.rb
class User < ActiveRecord::Base
  has_many :services, :through => :subscriptions
  has_many :subscriptions, :accessible => true
  accepts_nested_attributes_for :subscriptions
end

# service.rb
class Service < ActiveRecord::Base
  has_many :users, :through => :subscriptions
  has_many :subscriptions
end

# subscription.rb
class Subscription < ActiveRecord::Base
  belongs_to :user
  belongs_to :service
end

订阅还有一个 bool 列“通知”，我需要单独配置它，所以我查看了 API , 按照示例并为我的表单提出了以下代码:

- if current_user.subscriptions.length > 0
  %fieldset#subscriptions
    %legend Abonnements
    %table
      %tr
        %th.name
        %th.notification Notifications?
      - for subscription in current_user.subscriptions do
        %tr
          - f.fields_for :subscriptions, subscription do |s|
            %td=subscription.service.name
            %td= s.check_box :notification

但是当我保存表单时，所有关联的订阅都被销毁了。而当我选中复选框时，它不会被删除，但复选框也没有保存。有谁知道我做错了什么？

Answer 1

在尝试了将近 2 小时后，我终于让它工作了。对您的代码稍作更改就足够了:

# _form.html.haml
# […]
- if current_user.subscriptions.length > 0
  %fieldset#subscriptions
    %legend Abonnements
    %table
      %tr
        %th.name
        %th.notification Notifications?
      - f.fields_for :subscriptions do |sub|
        %tr
          %td= sub.object.service.name
          %td 
            = sub.check_box :notification
            = hidden_field_tag "user[service_ids][]", sub.object.service.id
# […]

因为 params[:user][:service_ids] 是空的，它删除了整个关联。