以两种不同的方式访问has_many关系ActiveRecord Rails

Question

我需要通过两种方式访问​​机构。 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 

的我的设置是这样的模式是，人可以在不同的机构学习，所以为了这个，我设置

has_many :institutions, :through => :institution_people 

的人模型

但在同一时间人可以有机构选择，所以我设置

has_many :institutions, :through => :institution_choices 

为人模型。

我应该如何建立人与机构之间的模型和联系，以便我可以从两种方式找到人的机构。

眼下

Person.first.institutions 

从institution_people表认为，正如

has_many :institutions, :through => :institution_people 

是在开始的时候我猜。

欢迎其他一些技术，以便我可以在两种方式获得机构。

Answer 1

在你Person模型，试试这个：

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，你需要某种接口在这里。我会做什么：

在机构模型：

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] 

（它加入从下面Person.rb查询（范围））

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]) 

（这应该从两个表中检索所有机构ID）

丑陋地狱，但仍然可能工作。你可以使用然后像：Institution.institutions_of(current_user)

Answer 3

如果您不需要保持结果作为ActiveRelation

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

    def institutions 
    institution_people + institution_choices 
    end 
end 

如果您确实需要保持它（为了调用person.institutions.order（ 'name'），那么它更复杂：

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