将多对多多态关联更改为一对多答案

【问题标题】：Change many to many polymorphics association to one to many将多对多多态关联更改为一对多
【发布时间】：2016-04-06 01:42:09
【问题描述】：

用户和活动与职业有多对多关联。我想将与用户的职业关联更改为多对一。如何修改？

用户

has_many :common_occupations, :as => :profession
has_many :occupations, :through => :common_occupations

职业

class Occupation < ActiveRecord::Base
has_many :users, :through => :common_occupations, :source => :profession, :source_type => "User"
has_many :campaigns, :through => :common_occupations, :source => :profession, :source_type => "Campaign"
has_many :common_occupations

广告系列

has_many :common_occupations, :as => :profession
has_many :occupations, :through => :common_occupations

普通职业

belongs_to :occupation
belongs_to :profession, :polymorphic => true

【问题讨论】：

标签： ruby-on-rails ruby activerecord ruby-on-rails-3.2

【解决方案1】：

用户

has_many :common_occupations, :as => :profession
belongs_to :occupation

职业

has_many :users
has_many :campaigns, :through => :common_occupations, :source => :profession, :source_type => "Campaign"
has_many :common_occupations

广告系列

has_many :common_occupations, :as => :profession
has_one :occupation, :through => :common_occupations

普通职业

belongs_to :occupation
belongs_to :profession, :polymorphic => true

此外，您必须将occupation_id 列添加到users 表中。

此外，之后您可以删除职业多态关联，因为它将不再需要。

【讨论】：

【解决方案2】：

最简单的方法是使用has_one 而不是has_many：

class User < AR::Base
  has_one :common_occupation, :as => :profession
  has_one :occupation, :through => :common_occupation

【讨论】：