的has_many：通过问题 [英] has_many :through questions

问题描述

我是previously使用has_and_belongs_to_many，并已转化为HAS_MANY：通过。下面是它的外观为游戏，可以有很多的用户播放列表。有了这个，我可以做game.users和user.games ....：

I was previously using has_and_belongs_to_many, and have converted to has_many :through. Here's how it looks for a list of games that can have many users playing. With this, I can do game.users and user.games....:

class Game < ActiveRecord::Base
 has_many :game_users, :dependent => :destroy
 has_many :users, :through => :game_users, :uniq => true
end

class User < ActiveRecord::Base
 has_many :game_users, :dependent => :destroy
 has_many :games, :through => :game_users, :uniq => true
end

class GameUser < ActiveRecord::Base
  belongs_to :game
  belongs_to :user
end

和用于连接表我的数据库迁移：

And my database migration for the join table:

create_table :game_users, :id => false do |t|
      t.column :game_id, :integer
      t.column :user_id, :integer
      t.column :player_index, :integer
    end

我不太确定我得到这一切，请帮我查一下我的情况：

I'm not quite sure I get all this, please help me check my facts:

1. 是因=>：摧毁是否正确？我想'game_users如果加盟无论是游戏还是用户被破坏的表项将被删除 - ？但我不想，如果游戏被删除的用户将被删除，反之亦然......

1. Is the dependent => :destroy correct? I want the 'game_users' join table entry to be deleted if either the game or the user is destroyed - but I don't want users to be deleted if games are deleted and vice versa..... ?

该Uniq字段应该说，比赛只包含独特的用户，而用户只包含独特的游戏。这是否正确？

The uniq field is supposed to say that games contain only unique users, and the users only contain unique games. Is that correct?

数据库迁移像以前那样有：ID =>假的。是不是仍然是正确的事是什么？我试着在控制台摧毁一个游戏，并得到有关失踪ID的抱怨......所以我猜不会和试图理解为什么。

The database migration as before has :id => false. Is that still the right thing to do? I tried in the console destroying a game, and got complaints about the missing id... so I'm guessing not and trying to understand why.

我觉得轨活动记录的关联非常混乱。我猜他们是不应该！

I find rails active record associations very confusing. I guess they aren't supposed to be!

推荐答案

1：是的，这是正确的。

1: Yes, that's correct

2：从上uniq中的文档：

2: From the documentation on uniq:

如果属实，副本将被省略   从集合。有用的   会同：通过

If true, duplicates will be omitted from the collection. Useful in conjunction with :through.

所以，是的，如果你的目标是进不去游戏的用户收集相同的游戏用户的游戏收集，也没有相同的用户，这是正确的。这一切都说明这里。

So, yes, if you aim is not get the same game in User's games-collection nor the same user in Game's users-collection, that's correct. It's all explained here.

它不会，但是，要创建从prevent重复GameUsers。对于这一点，你需要使用<一个href="http://apidock.com/rails/ActiveRecord/Validations/ClassMethods/validates%5Funiqueness%5Fof">validates_在GameUser模型的唯一性_of ：

It will not, however, prevent duplicate GameUsers from being created. For that, you'd need to use validates_ uniqueness _of in the GameUser-model:

class GameUser < ActiveRecord::Base
  validates_uniqueness_of :game_id, :scope => :user_id
end

3：不，你不希望使用：ID =>假了。通过从has_and_belongs_to_many切换到HAS_MANY：通过，你已经晋升的许多一对多连接表，以一个完整的模型 - GameUser - 这都需要有自己的ID

3: No, you don't want to use :id => false any more. By switching from has_and_belongs_to_many to has_many :through, you have promoted your many-to-many join-table to a full model - GameUser - which requires its own id.

虽然是旧的，这仍是一个好文章理解的has_many：通过。

While it is old, this is still a good article for understanding has_many :through.

这篇关于的has_many：通过问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！