Rails有许多和属于 [英] Rails has many and belongs to

问题描述

在M. Hartly的教程中，我了解了模型及其关系的概念（微博belongs_to用户，以及用户has_many微博）。

然而，我不确定如何在日常交易项目中付诸实践。

我决定为拥有不同权利的两种用户类型的用户建立一个模型： b
$ b

• admin_user谁可以创建/更新/编辑/删除交易




• 可以看到交易的standard_user以及他们是否有兴趣参与交易

两位用户都进入用户数据库

我也决定拥有一个交易模型，并进入交易数据库
所以我理解得很好：

• a admin_user has_many deals




• 交易属于admin_user




• standard_user有很多交易（事实上他可以参与在很多交易中都是如此）
  

• 并且交易不属于standard_user，因此我无法在此处说出任何内容。

我的理解是正确的吗？可以根据用户的权利类型来定义与模型对象的不同关系（在这种情况下为交易）：

PS：我想我会分开使用cancan gem的用户可以给他们不同的权限

解决方案

您所描述的最大问题是standard_user has_many：交易，但交易不属于standard_user;他们可能同时被许多标准用户使用。这意味着交易不能 belongs_to 标准用户，因为您的交易中不能有 standard_user_id >列表（因为您需要任意多列来处理可能参与的任意多用户）。

为了获得像这样的多对多关系，你需要一个链接表。这里有一个方法可以在Rails中实现：

  class DealParticipation< ActiveRecord：Base 
＃这意味着deal_participations表有一个standard_user_id键
 belongs_to：standard_user 
＃这意味着deal_participations表有一个deal_id键
 belongs_to：deal 
 
＃...更多的逻辑去这里... 
 end 
  

现在你的标准用户看起来像：

  class StandardUser< ActiveRecord :: Base 
 has_many：deal_participations 
 has_many：deals，：through => ：deal_participations 
＃... more logic goes here ... 
 end 
  

您的交易类看起来像：

  class Deal< ActiveRecord :: Base 
 has_many：deal_participations 
 has_many：standard_users，：through => ：deal_participations 
 belongs_to：admin_user 
＃...更多逻辑在这里... 
结束
  

然后，您需要三张表：一张用于交易，一张用于 deal_participations ，和一个用于 standard_users （加上管理员用户的东西）。

根据您的需要，您可能还想尝试使用单表继承（STI）使用户和管理用户从一个公共基类派生。您可以阅读更多关于STI 此处的信息。

我希望有所帮助！享受Rails入门！

I am building a daily deal app to better learn Ruby on Rails.

On M. Hartly tutorial, I understood the concept of models and their relationship (a microposts belongs_to a user, and a user has_many microposts).

However I am not sure how to put that into practice on my daily deal project.

I decided to have a Model for users with two type of users with different rights:

• admin_user who can create/update/edit/delete the deals

• standard_user who can see the deals and if they find one interesting participate in a deal

Both users go into the users database

I also decided to have a model for deals and go in the Deals database So have I understood well:

• a admin_user has_many deals

• deals belongs to a admin_user

• standard_user has many deals (indeed he can participate in many deals)

• and deals do NOT belong to standard_user so I can’t say anything here.

Have I understood things right? It is possible to define according to the type of right of a user different relationship to a model object(in this case: deals)

PS: I think I’ll separate users with cancan gem to give them different rights

解决方案

The biggest issue with what you're describing is that a standard_user has_many :deals, but deals don't belong to a standard_user; they probably are in use by many standard users at the same time. That means that a deal can't belong_to a standard_user, because you can't have a standard_user_id column in your Deals table (since you'd need arbitrarily many columns to deal with the arbitrarily many users who might participate).

In order to have a many-to-many relationship like this, you need a link table. Here's one way to achieve this in Rails:

class DealParticipation < ActiveRecord:Base
  #This means the deal_participations table has a standard_user_id key
  belongs_to :standard_user
  #This means the deal_participations table has a deal_id key
  belongs_to :deal

  #... more logic goes here ...
end

Now your standard user looks like:

class StandardUser < ActiveRecord::Base
  has_many :deal_participations
  has_many :deals, :through => :deal_participations
  # ... more logic goes here ...
end

And your deal class looks like:

class Deal < ActiveRecord::Base
  has_many :deal_participations
  has_many :standard_users, :through => :deal_participations
  belongs_to :admin_user
  #... more logic goes here ...
end

You'll then need three tables: one for deals, one for deal_participations, and one for standard_users (plus the stuff for admin users).

Depending on your needs, you may also want to try using single-table inheritance (STI) to make Users and Admin Users derive from a common base class. You can read more about STI here.

I hope that helps! Enjoy getting started with Rails!

这篇关于Rails有许多和属于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！