Rails 4：组合 has_many :through association with polymorphic association

Question

在我的 Rails 4 应用程序中，我有以下模型：

User
has_many :administrations
has_many :calendars, through: :administrations
has_many :comments
has_many :calendar_comments, through: :calendars, :source => :comments

Calendar
has_many :administrations
has_many :users, through: :administrations
has_many :posts
has_many :comments, through: posts
has_many :ads

Administration
belongs_to :user
belongs_to :calendar

Post
belongs_to :calendar
has_many :comments, as: :commentable

Ad
belongs_to :calendar
has_many :comments, as: :commentable

Comment
belongs_to :commentable, polymorphic: true
belongs_to :user

我需要从 calendar ad belongs_to.[=47= 访问 comments belong_to 和 ad ]

这就是我在 Calendars#Index 操作中尝试做的事情：

@posts_comments = @user.calendar_comments.where(commentable_type: "Post").order("created_at DESC").limit(5)
@ads_comments = @user.calendar_comments.where(commentable_type: "Ad").order("created_at DESC").limit(5)

我的第一个猜测是在日历模型中添加 has_many :comments, through: ads：

Calendar
has_many :administrations
has_many :users, through: :administrations
has_many :posts
has_many :comments, through: posts
has_many : ads
has_many :comments, through: ads

但这取消了 has_many :comments, through: posts 的效果，然后我无法再从 calendar 访问 belong_to 和 post 的 comments post belongs_to.

有没有办法让 BOTH has_many :comments, through: posts AND has_many :comments, through: ads 工作？

——————

更新：根据this article and that Stack Overflow question，答案可能在于使用source:和source_type:。

但是不确定如何使用它们。

——————

更新 2：以下代码是否有意义？

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :commented_posts, through: :comments, source: :commentable, source_type: 'Post'
  has_many :ads, dependent: :destroy
  has_many :commented_ads, through: :comments, source: :commentable, source_type: 'Ad'

——————

更新 3：当我尝试上面的代码时，我收到以下错误消息：

Could not find the source association(s) :comments in model Calendar. Try 'has_many :calendar_comments, :through => :calendars, :source => <name>'. Is it one of administrations, users, posts, commented_posts, ads, commented_ads, invites, or pokes?

我尝试了以下方法：

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :calendar_comments, :through => :calendars, :source => :post
  has_many :ads, dependent: :destroy
  has_many :calendar_comments, :through => :calendars, :source => :ad

——————

更新 4：新的失败尝试，代码如下：

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :calendar_comments, :through => :commentable, :source => :post
  has_many :ads, dependent: :destroy
  has_many :calendar_comments, :through => :commentable, :source => :ad

仍然无法正常工作，与上面相同的错误消息。

——————

更新 5：根据 MrYoshiji 的回答，我现在有

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :posts_comments, through: :posts, source_type: 'Post'
  has_many :ads, dependent: :destroy
  has_many :ads_comments, through: :ads, source_type: 'Ad'

现在，User 模型中的 has_many :calendar_comments, through: :calendars, :source => :comments 不再有效。

我试过了：

has_many :comments
has_many :calendar_post_comments, through: :calendars, :source => :post_comments
has_many :calendar_ad_comments, through: :calendars, :source => :ad_comments

还是不行。

——————

更新 6：我仍然被这个问题所困扰，因为我无法找到让以下代码工作的方法：

@posts_comments = @user.calendar_comments.where(commentable_type: "Post").order("created_at DESC").limit(5)
@ads_comments = @user.calendar_comments.where(commentable_type: "Ad").order("created_at DESC").limit(5)

我尝试了很多不同的东西，到目前为止我能想到的最好的是：

class Calendar < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :users, through: :administrations
  has_many :posts, dependent: :destroy
  has_many :post_comments, through: :posts, source_type: 'Post'
  has_many :ads, dependent: :destroy
  has_many :ad_comments, through: :ads, source_type: 'Ad'
end

class User < ActiveRecord::Base
  has_many :administrations, dependent: :destroy
  has_many :calendars, through: :administrations
  has_many :comments
  has_many :calendar_post_comments, through: :calendars, :source => :post_comments
  has_many :calendar_ad_comments, through: :calendars, :source => :ad_comments
end

然后，我按如下方式更新我的日历控制器：

def index
    @user = current_user
    @calendars = @user.calendars.all
    @posts_comments = @user.calendar_post_comments
                              .order("created_at DESC")
                              .limit(5)
    @ads_comments = @user.calendar_ad.comments
                              .order("created_at DESC")
                              .limit(5)
end

但是这个returns出现如下错误：

NoMethodError at /calendars
undefined method `chain' for nil:NilClass
@posts_comments = @user.calendar_post_comments.order("created_at DESC").limit(5)

这里有什么问题？

Answer 1

您应该尝试以下操作：

class Calendar < ActiveRecord::Base
  # [ ... ]
  has_many :posts
  has_many :posts_comments, through: posts, source_type: 'Post'
  has_many :ads
  has_many :ads_comments, through: ads, source_type: 'Ad'

考虑到 Ad 和 Post 模型都具有以下特点：

has_many :comments, as: :commentable

Rails 4：组合 has_many :through association with polymorphic association

Rails 4: combining has_many :through association with polymorphic association

activerecord

ruby-on-rails

has-many-through

polymorphic-associations

ruby-on-rails-4