如何在 Rails 中自动对 has_many 关系进行排序? [英] How do I automatically sort a has_many relationship in Rails?

问题描述

这似乎是一个非常简单的问题，但我在任何地方都没有看到它的答案.

This seems like a really simple question but I haven't seen it answered anywhere.

在 Rails 中，如果您有:

In rails if you have:

class Article < ActiveRecord::Base 
  has_many :comments 
end 
class Comments < ActiveRecord::Base 
  belongs_to :article 
end

为什么你不能用这样的东西对评论进行排序:

Why can't you order the comments with something like this:

@article.comments(:order=>"created_at DESC")

如果您需要大量引用命名范围，甚至人们也会这样做:

Named scope works if you need to reference it a lot and even people do stuff like this:

@article.comments.sort { |x,y| x.created_at <=> y.created_at }

但有些东西告诉我它应该更简单.我错过了什么?

But something tells me it should be simpler. What am I missing?

推荐答案

您可以使用 has_many 本身的选项指定裸集合的排序顺序:

You can specify the sort order for the bare collection with an option on has_many itself:

class Article < ActiveRecord::Base 
  has_many :comments, :order => 'created_at DESC'
end 
class Comment < ActiveRecord::Base 
  belongs_to :article 
end

或者，如果您想要一种简单的、非数据库的排序方法，请使用 sort_by:

Or, if you want a simple, non-database method of sorting, use sort_by:

article.comments.sort_by &:created_at

使用 ActiveRecord 添加的排序方法收集:

Collecting this with the ActiveRecord-added methods of ordering:

article.comments.find(:all, :order => 'created_at DESC')
article.comments.all(:order => 'created_at DESC')

您的进展可能会有所不同:上述解决方案的性能特征会发生巨大变化，具体取决于您最初获取数据的方式以及您使用哪种 Ruby 来运行您的应用.

Your mileage may vary: the performance characteristics of the above solutions will change wildly depending on how you're fetching data in the first place and which Ruby you're using to run your app.

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