任何方式使用AREL定制联想？ [英] Any way to use AREL for custom associations?

问题描述

model Post
  # ActiveRecord associations have tons of options that let
  # you do just about anything like:
  has_many :comments
  has_many :spam_comments, :conditions => ['spammy = ?', true]

  # In Rails 3, named scopes are ultra-elegant, and let you do things like:
  scope :with_comments, joins(:comments)
end

有没有办法使用AREL，或以其他方式精简语法，为优雅的定义自定义协会评为命名范围？

Is there any way to use AREL, or an otherwise leaner syntax, to define custom associations as elegantly as named scopes?

更新

我已经决定这是不是一个好主意，把那种细节到一个协会，无论如何，因为协会应始终/大部分定义模型之间的基本关系。

I've decided it's not a good idea to put that sort of detail into an association anyway, because associations should always/mostly define the basic relationships between models.

推荐答案

解决的办法之一就是把对垃圾邮件的评论范围：

One of the solutions is to put spammy scope on Comments:

model Post
  has_many :comments

  scope :with_comments, joins(:comments)
end

model Comment
  scope :spammy, where(:spammy => true)
end

这看起来对于责任的模拟了一下清洁。性能方面它是完全一样的：

This looks a bit cleaner with respect to model responsibilities. Performance-wise it's exactly the same:

p.comments.spammy.to_sql
# → SELECT "comments".* FROM "comments"
#   WHERE ("comments".post_id = 2) AND ("comments"."spammy" = "t")

附加的好处：你可以得到垃圾邮件的评论从任何其他协会

The added benefit: you can get spammy comments from any other associations.

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