Rails 4:结合has_many:通过与多态关联相关联

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

我需要访问comments的是belong_to一个ad从calendar的ad belongs_to.

这就是我在Calendars#Index行动中要做的事情:

@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)

我的第一个猜测是添加has_many :comments, through: ads日历模型:

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

但是,取消的影响has_many :comments, through: posts,然后我再也无法访问comments是belong_to一个post从calendar的post belongs_to.

有没有办法兼顾 has_many :comments, through: posts 和 has_many :comments, through: ads工作？

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更新:根据这篇文章和Stack Overflow问题,答案可能在于使用source:和source_type:.

但不确定如何使用它们.

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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'

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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

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更新4:使用以下代码的新尝试失败:

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

仍然没有工作,与上面相同的错误信息.

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更新5:根据Mr.Yoshiji的回答,我现在有了

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,has_many :calendar_comments, through: :calendars, :source => :comments在User模型中不再有效.

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

还是行不通.

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更新6:我仍然坚持这个问题,因为我无法弄清楚如何使以下代码工作:

@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Calendars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

但是这会返回以下错误:

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

这有什么不对？

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