过滤多态belongs_to关系答案

【问题标题】：Filtering polymorphic belongs_to relations过滤多态belongs_to关系
【发布时间】：2015-03-02 21:19:22
【问题描述】：

假设我有这些模型：

class Image < ActiveRecord::Base
  has_many :attachments, as: :attachable
end

class File < ActiveRecord::Base
  has_many :attachments, as: :attachable
end

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

  # How can I add an image relation?
  belongs_to :image ...
  belongs_to :file ...
end

将图像/文件关系添加到附件模型的最佳方法是什么

这就是我最终想要实现的目标：

class Page < ActiveRecord::Base
  has_many :attachments, as: :attacher

  # ?
  has_many :images, 
  has_many :files
end

【问题讨论】：

标签： ruby-on-rails activerecord polymorphism

【解决方案1】：

如果我的图片链接 = 你的附件，我的图片 = 你的页面，我的项目 = 你的图片，我的场景 = 你的文件（或者它已经太久了，我不记得我自己的代码正确），也许类似于此。

class Project
  has_many :imagelinks, :as => :displayable, :dependent => :destroy
  has_many :images, :through => :imagelinks
end

class Scenario
  has_many :imagelinks, :as => :displayable, :dependent => :destroy
  has_many :images, :through => :imagelinks
end

class Unittest
  has_many :imagelinks, :as => :displayable, :dependent => :destroy
  has_many :images, :through => :imagelinks
end

class Imagelink
  # attributes: id, image_id, displayable_id, displayable_type
  belongs_to :image
  belongs_to :displayable, :polymorphic => true
  belongs_to :project, :class_name => 'Project', :foreign_key => 'displayable_id'
  belongs_to :scenario, :class_name => 'Scenario', :foreign_key => 'displayable_id'
  belongs_to :unites, :class_name => 'Unittest', :foreign_key => 'displayable_id'
end

class Image
  has_many :imagelinks, :dependent => :destroy
  has_many :projects, :through => :imagelinks, :source => :project, :conditions => "imagelinks.displayable_type = 'Project'"
  has_many :scenarios, :through => :imagelinks, :source => :scenario, :conditions => "imagelinks.displayable_type = 'Scenario'"
  has_many :unittests, :through => :imagelinks, :source => :unittest, :conditions => "imagelinks.displayable_type = 'Unittest'"
  has_attached_file :asset, :styles => { blah blah blah }
end

【讨论】：