递归树构建函数仅映射一个孩子(Recursive tree-building function only maps over one child)

 我试图递归构建一棵树。 下面的类通过递归调用.children getter将树构建到Hash中。 
 
class Tree
  attr_reader :root

  def initialize(uri:)
    @root     = Article.new(uri: uri)
    @children = nil
  end

  def children(depth: 3, article_children: self.root.child_links)
    @children ||= article_children.map do |uri|
      puts "URI: #{uri}"
      if (depth == 0)
        return Article.new(uri: uri)
      else
        article = Article.new(uri: uri)
        return { article => self.children(depth: depth - 1, article_children: article.child_links) }
      end
    end

    puts JSON.pretty_generate(@children)
    return @children
  end
end
 
 我期望得到的JSON看起来像这样： 
 
{
      "#<Article:0x00007ff1a33c06d0>": {
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
      }
    }
}
 
 然而，美化的JSON最终看起来像这样： 
 
{
  "#<Article:0x00007ff1a33c06d0>": {
    "#<Article:0x00007ff1a345e920>": {
      "#<Article:0x00007ff1a3989418>": "#<Article:0x00007ff1a423f698>"
    }
  }
}
 
 并在article.children.map输出中puts "URI: #{uri} 
 
URI: https://child.uri.org/example/uri
URI: https://child.uri.org/example/uri1
URI: https://child.uri.org/example/uri2
URI: https://child.uri.org/example/uri3
 
 每个URI都是每个项目对象的第一个子URI。 
 
 为什么map仅处理第一个元素，而不处理整个数组？ 

I'm attempting to recursively build a tree. The following class builds the tree into a Hash by recursively calling the .children getter.
 
class Tree
  attr_reader :root

  def initialize(uri:)
    @root     = Article.new(uri: uri)
    @children = nil
  end

  def children(depth: 3, article_children: self.root.child_links)
    @children ||= article_children.map do |uri|
      puts "URI: #{uri}"
      if (depth == 0)
        return Article.new(uri: uri)
      else
        article = Article.new(uri: uri)
        return { article => self.children(depth: depth - 1, article_children: article.child_links) }
      end
    end

    puts JSON.pretty_generate(@children)
    return @children
  end
end
 
I expect the resulting JSON to look something like this:
 
{
      "#<Article:0x00007ff1a33c06d0>": {
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
        "#<Article:0x00007ff1a345e920>": {
          "#<Article:0x00007ff1a3989418>": ["#<Article:0x00007ff1a423f698>", ...]
        },
      }
    }
}
 
However, the prettified JSON ends up looking like this:
 
{
  "#<Article:0x00007ff1a33c06d0>": {
    "#<Article:0x00007ff1a345e920>": {
      "#<Article:0x00007ff1a3989418>": "#<Article:0x00007ff1a423f698>"
    }
  }
}
 
And puts "URI: #{uri} within article.children.map outputs
 
URI: https://child.uri.org/example/uri
URI: https://child.uri.org/example/uri1
URI: https://child.uri.org/example/uri2
URI: https://child.uri.org/example/uri3
 
Each of these URIs is the first child URI of each article object.
 
Why is map only processing the first element, and not the entirety of the array?

原文：https://stackoverflow.com/questions/49787048