以兩種不同的方式訪問has_many關係ActiveRecord Rails

Question

我需要通過兩種方式訪問​​機構。 我的模型如下：

class Person < ActiveRecord::Base 
    has_many :institution_people 
    has_many :institution_choices 
    has_many :institutions, :through => :institution_people 
    has_many :institutions, :through => :institution_choices 
    fields........ 
end 

class Institution < ActiveRecord::Base 
    has_many :people, :through => :institution_people 
    has_many :people, :through => :institution_choices 
    has_many :institution_people 
    has_many :institution_choices 
end 

class InstitutionChoice < ActiveRecord::Base 
    belongs_to :person 
    belongs_to :institution 
end 

class InstitutionPerson < ActiveRecord::Base 
    belongs_to :person 
    belongs_to :institution 
end 

的我的設置是這樣的模式是，人可以在不同的機構學習，所以爲了這個，我設置

has_many :institutions, :through => :institution_people 

的人模型

但在同一時間人可以有機構選擇，所以我設置

has_many :institutions, :through => :institution_choices 

爲人模型。

我應該如何建立人與機構之間的模型和聯繫，以便我可以從兩種方式找到人的機構。

眼下

Person.first.institutions 

從institution_people表認爲，正如

has_many :institutions, :through => :institution_people 

是在開始的時候我猜。

歡迎其他一些技術，以便我可以在兩種方式獲得機構。

Answer 1

在你Person模型，試試這個：

class Person < ActiveRecord::Base 
    has_many :institution_people 
    has_many :institution_choices 
    has_many :institutions_people, :through => :institution_people, :source => :institutions, :class_name => "Institution" 
    has_many :institutions_choices, :through => :institution_choices, :source => :institutions, :class_name => "Institution" 
end 

http://guides.rubyonrails.org/association_basics.html#has_many-association-reference

Answer 2

基本上，你需要某種接口在這裏。我會做什麼：

在機構模型：

scope :institutions_of, proc { |person| joins(' INNER JOIN (' + Person.institution_ids(person) + ') q 
    ON institutions.id = q.ip_iid OR institutions.id = q.ic_iid').where(['institutions.person_id = ?', person_id] 

（它加入從下面Person.rb查詢（範圍））

在Person.rb

：

scope :institution_ids, proc { |person| select('ip.institution_id ip_idd, ic.institution_id ic_idd 
from institution_people ip 
inner join institution_choice ic on ip.person_id = ic.person_id'). 
where(['ip.person_id = ?', person.id]) 

（這應該從兩個表中檢索所有機構ID）

醜陋地獄，但仍然可能工作。你可以使用然後像：Institution.institutions_of(current_user)

Answer 3

如果您不需要保持結果作爲ActiveRelation

class Person < ActiveRecord::Base 
    has_many :institution_people 
    has_many :institution_choices 

    def institutions 
    institution_people + institution_choices 
    end 
end 

如果您確實需要保持它（爲了調用person.institutions.order（ 'name'），那麼它更復雜：

class Person < ActiveRecord::Base 
    has_many :institution_people 
    has_many :institution_choices 

    scope :institutions, :select => 'select * from (select * from institution_people union all select * from institution_choices) as institutions' 
end