轨态关联参考

Question

我有一个多态关联对我的用户模型

class User < ActiveRecord::Base 
    has_many :attachments, as: :attachable 

的如下

class Attachment < ActiveRecord::Base 
    belongs_to :attachable, polymorphic: true 
    has_attached_file :file 
end 

然后，我希望能够做到以下几点

attachment = Attachment.create(:file => params[:attachment]) 
attachment.user = current_user 

但我得到一个

*** NoMethodError Exception: undefined method `user=' for #<Attachment:0x007fee92901ce8> 

Answer 1

的attachment属于attachable（它是多晶型）。设置正确的方法是这样做的：

attachment.attachable = current_user 

---

我强烈建议您重新命名关系以下几点：

class Attachment < ActiveRecord::Base 
    belongs_to :owner, polymorphic: true 

class User < ActiveRecord::Base 
    has_many :attachments, as: :owner 

因为关系的名字owner的方法更多明确的比attachable。见自己：

# What is easier to understan? 
attachment.attachable = current_user 
# or 
attachment.owner = current_user 

Answer 2

不能引用的多态关系的方式。它不得不是

attachment.attachable = current_user