问题描述
我有以下的车型。用户有UserActions，和一个可能UserAction可以是ContactAction（UserAction是一个多态性）。有喜欢的LoginAction等于是
I have the following models. Users have UserActions, and one possible UserAction can be a ContactAction (UserAction is a polymorphism). There are other actions like LoginAction etc. So
class User < AR::Base
has_many :contact_requests, :class_name => "ContactAction"
has_many :user_actions
has_many_polymorphs :user_actionables, :from => [:contact_actions, ...], :through => :user_actions
end
class UserAction < AR::Base
belongs_to :user
belongs_to :user_actionable, :polymorphic => true
end
class ContactAction < AR::Base
belongs_to :user
named_scope :pending, ...
named_scope :active, ...
end
的想法是，一个ContactAction连接两个用户（与其它后果在应用内），并总是具有接收和发送端。与此同时，一个ContactAction可以有不同的状态，例如过期，等待等。
The idea is that a ContactAction joins two users (with other consequences within the app) and always has a receiving and a sending end. At the same time, a ContactAction can have different states, e.g. expired, pending, etc.
我可以说 @ user.contact_actions.pending 或 @ user.contact_requests.expired 来列出所有未决/过期请求的用户已发送或接收。这工作得很好。
I can say @user.contact_actions.pending or @user.contact_requests.expired to list all pending / expired requests a user has sent or received. This works fine.
我现在想一个办法的加入这两种类型的ContactAction的。即 @ user.contact_actions_or_requests 。我试过如下：
What I would now like is a way to join both types of ContactAction. I.e. @user.contact_actions_or_requests. I tried the following:
class User
def contact_actions_or_requests
self.contact_actions + self.contact_requests
end
# or
has_many :contact_actions_or_requests, :finder_sql => ..., :counter_sql => ...
end
，但所有这些都认为是不可能使用额外的发现者或named_scopes上的关联，例如顶部的问题 @ user.contact_actions_or_requests.find（...）或 @ user.contact_actions_or_requests.expired 。
基本上，我需要一种方法来恩preSS 1：n的协会，有两种不同的路径。一个是用户 - > ContactAction.user_id ，另一个是用户 - > UserAction.user_id - > UserAction.user_actionable_id - > ContactAction.id 。然后加入一个单一的列表的结果（ContactActions）与named_scopes和/或发现者进一步处理。
Basically, I need a way to express a 1:n association which has two different paths. One is User -> ContactAction.user_id, the other is User -> UserAction.user_id -> UserAction.user_actionable_id -> ContactAction.id. And then join the results (ContactActions) in one single list for further processing with named_scopes and/or finders.
因为我需要这个协会在字面上几十个地方，这将是写一个大麻烦（和维护！），每案自定义的SQL。
Since I need this association in literally dozens of places, it would be a major hassle to write (and maintain!) custom SQL for every case.
我想preFER在Rails中解决这个问题，但我也开放给其他建议（例如一个PostgreSQL 8.3的程序或某事这类似于）。重要的是，在年底，我可以使用的Rails的便利功能，如与其他任何联系，更重要的是，还巢他们。
I would prefer to solve this in Rails, but I am also open to other suggestions (e.g. a PostgreSQL 8.3 procedure or something simliar). The important thing is that in the end, I can use Rails's convenience functions like with any other association, and more importantly, also nest them.
任何想法将非常AP preciated。
Any ideas would be very much appreciated.
感谢您！
要以我自己的问题提供一个答案排序的：
To provide a sort-of answer to my own question:
我可能会解决这个使用数据库视图，并根据需要添加相应的关联。针对上述情况，我可以
I will probably solve this using a database view and add appropriate associations as needed. For the above, I can
- 使用SQL在finder_sql创建视图，
- 将其命名为contact_actions_or_requests，
- 修改SELECT子句中添加user_id列，
- 添加应用程序/模型/ ContactActionsOrRequests.rb，
- ，然后添加的has_many：contact_actions_or_requests来user.rb
我不知道我怎么会处理更新记录，但 - 这似乎并不可能，以期 - 但也许这是第一启动
I don't know how I'll handle updating records yet - this seems not to be possible with a view - but maybe this is a first start.
推荐答案
您正在寻找的方法是合并。如果你有两个的ActiveRecord ::关系，R1和R2，可以调用r1.merge（R2）来获得，它结合了两个新的ActiveRecord ::关系的对象。
The method you are looking for is merge. If you have two ActiveRecord::Relations, r1 and r2, you can call r1.merge(r2) to get a new ActiveRecord::Relation object that combines the two.
如果这会为你工作在你的范围如何设置在很大程度上取决于，如果你可以改变他们产生有意义的结果。让我们看几个例子：
If this will work for you depends largely on how your scopes are set up and if you can change them to produce a meaningful result. Let's look at a few examples:
假设你有一个页面模型。它有正常的created_at和属性的updated_at，所以我们可以有这样的范围：
：更新 - > {其中（'！created_at =的updated_at'）}
：not_updated - > {其中（'created_at =的updated_at'）}
Suppose you have a Page model. It has the normal created_at and updated_at attributes, so we could have scopes like::updated -> { where('created_at != updated_at') }:not_updated -> { where('created_at = updated_at') }
如果你拉这从数据库中，你会得到：
If you pull this out of the database you'll get:
r1 = Page.updated # SELECT `pages`.* FROM `pages` WHERE (created_at != updated_at)
r2 = Page.not_updated # SELECT `pages`.* FROM `pages` WHERE (created_at = updated_at)
r1.merge(r2) # SELECT `pages`.* FROM `pages` WHERE (created_at != updated_at) AND (created_at = updated_at)
=> []
因此它没有将两者结合起来的关系，但不能以有意义的方式。另一个问题：
So it did combine the two relations, but not in a meaningful way. Another one:
r1 = Page.where( :name => "Test1" ) # SELECT `pages`.* FROM `pages` WHERE `pages`.`name` = 'Test1'
r2 = Page.where( :name => "Test2" ) # SELECT `pages`.* FROM `pages` WHERE `pages`.`name` = 'Test2'
r1.merge(r2) # SELECT `pages`.* FROM `pages` WHERE `pages`.`name` = 'Test2'
因此，它可能为你工作，但也许不是，根据您的情况。
So, it might work for you, but maybe not, depending on your situation.
另外，同时建议，这样做的方法是创建您模型的新范围：
Another, and recommended, way of doing this is to create a new scope on you model:
class ContactAction < AR::Base
belongs_to :user
scope :pending, ...
scope :active, ...
scope :actions_and_requests, pending.active # Combine existing logic
scope :actions_and_requests, -> { ... } # Or, write a new scope with custom logic
end
，结合你想在一个查询收集不同的特质......
That combines the different traits you want to collect in one query ...
这篇关于Ruby on Rails的3：合并多个的has_many或has_many_through协会结果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！