Ruby 中嵌套/邻接模型的排序算法

发布于 2024-08-20 10:11:54 字数 285 浏览 5 评论 0原文

我一直在尝试找到一种好方法来做到这一点，无论是在客户端的 Javascript 中还是在服务器的最后一刻。这是一个 Rails 应用程序，但这是一个非常普遍的问题。我有一个分层模型，当前存储在嵌套集模型中。然后该模型具有：

parent_id, lft, and rgt

我想从数据库中提取一个 select 语句中的所有模型，因此给我一个简单的模型列表，然后将它们动态排序到树状层次结构中。我还没有找到一种不需要递归的干净方法来做到这一点。我确信有一个很好的算法可以解决这个问题。谢谢。

原文

I've been trying to find a good way of doing this, either on the client side in Javascript or at the last minute within the server. This is a Rails application but it is a pretty generic question. I have a model that is hierarchical, and is currently stored in a nested set model. The model then has:

parent_id, lft, and rgt

I would like to pull out all of the models in one select statement from the database, therefore giving me a flat list of models, and then sort them on the fly into a tree hierarchy. I have not found a clean way to do this that would not require recursion. I'm sure there is a nice algorithm out there for this. Thanks.

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扭转时空 2024-08-27 10:11:55

我不知道没有递归的算法。无论如何我想分享我的站点地图视图助手：

def tree_from_set(set, &node_text)
  buf = '<ul>'
  siblings = set.select{|n| n.parent_id == set[0].parent_id}

  siblings.each do |node|
    children = set.select{|n| n.lft > node.lft and n.rgt < node.rgt }
    buf << '<li>'
      if children.blank?
        buf << yield(node)
      else
        buf << yield(node)
        buf << tree_from_set(children, &node_text)
      end
    buf << '</li>'
  end
  buf << '</ul>'
end

I don't know of a algorithm without recursion. Thought i'd share my sitemap view helper anyhow:

def tree_from_set(set, &node_text)
  buf = '<ul>'
  siblings = set.select{|n| n.parent_id == set[0].parent_id}

  siblings.each do |node|
    children = set.select{|n| n.lft > node.lft and n.rgt < node.rgt }
    buf << '<li>'
      if children.blank?
        buf << yield(node)
      else
        buf << yield(node)
        buf << tree_from_set(children, &node_text)
      end
    buf << '</li>'
  end
  buf << '</ul>'
end

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