ruby如何生成树结构表单数组？

我有一个数组，其中包含如下项目列表

arr = [
  {:id=>1,  :title=>"A",      :parent_id=>nil}, 
  {:id=>2,  :title=>"B",      :parent_id=>nil},
  {:id=>3,  :title=>"A1",     :parent_id=>1}, 
  {:id=>4,  :title=>"A2",     :parent_id=>1},
  {:id=>5,  :title=>"A11",    :parent_id=>3}, 
  {:id=>6,  :title=>"12",     :parent_id=>3},
  {:id=>7,  :title=>"A2=121", :parent_id=>6}, 
  {:id=>8,  :title=>"A21",    :parent_id=>4},
  {:id=>9,  :title=>"B11",    :parent_id=>2}, 
  {:id=>10, :title=>"B12",    :parent_id=>2},
   ...
]

如果

parent\u id

是

nil

则其应为父节点，如果

parent\u id

不是

nil

则其应位于特定父节点下

基于

id

和

parent\u id

，我想提供如下响应：

-A
  -A1
    -A11
    -A12
      -A123
  -A2
    -A21
-B
  -B1
    -B11
    -B12

如何生成上面提到的响应

谢谢

您可以使用宝石，如：

hash_tree

提供了一种将子树呈现为有序结构的方法 嵌套哈希：

Tag.hash_tree
#=> {a => {b => {c1 => {d1 => {}}, c2 => {d2 => {}}}, b2 => {}}}

或：

祖先可以将整个子树排列成嵌套的散列，以便 从数据库检索后的导航<代码>树节点。排列可以 例如返回：

{ #<TreeNode id: 100018, name: "Stinky", ancestry: nil>
  => { #<TreeNode id: 100019, name: "Crunchy", ancestry: "100018">
    => { #<TreeNode id: 100020, name: "Squeeky", ancestry: "100018/100019">
      => {}
    }
  }
}

---

并非要取代经验证的宝石，但根据您的需要，您可以使用以下简单的产品：

groups = arr.group_by{ |x| x[:parent_id] }
groups.default = []

build_tree = 
  lambda do |parent| 
    [parent[:title], groups[parent[:id]].map(&build_tree)]
    # or
    # { parent[:title] => groups[parent[:id]].map(&build_tree) }
  end

p build_tree[:id => nil][1] # :id => nil is not required, empty hash will work too
# => [["A", [["A1", [["A11", []], ["A12", [["A122", []]]]]], ["A2", [["A21", []]]]]], ["B", [["B11", []], ["B12", []]]]]

一个例子：

#!/usr/bin/env ruby

root = {:id => 0, :title => '', :parent_id => nil}

arr = arr = [
  {:id=>1,  :title=>"A",      :parent_id=>nil}, 
  {:id=>2,  :title=>"B",      :parent_id=>nil},
  {:id=>3,  :title=>"A1",     :parent_id=>1}, 
  {:id=>4,  :title=>"A2",     :parent_id=>1},
  {:id=>5,  :title=>"A11",    :parent_id=>3}, 
  {:id=>6,  :title=>"12",     :parent_id=>3},
  {:id=>7,  :title=>"A2=121", :parent_id=>6}, 
  {:id=>8,  :title=>"A21",    :parent_id=>4},
  {:id=>9,  :title=>"B11",    :parent_id=>2}, 
  {:id=>10, :title=>"B12",    :parent_id=>2},
]

map = {}

arr.each do |e|
  map[e[:id]] = e
end

@@tree = {}

arr.each do |e|
  pid = e[:parent_id]
  if pid == nil || !map.has_key?(pid)
    (@@tree[root] ||= []) << e
  else
    (@@tree[map[pid]] ||= []) << e
  end
end

def print_tree(item, level)
  items = @@tree[item]
  unless items == nil
    indent = level > 0 ? sprintf("%#{level * 2}s", " ") : ""
    items.each do |e|
      puts "#{indent}-#{e[:title]}"
      print_tree(e, level + 1)
    end
  end
end

print_tree(root, 0)

---

这是Rails项目吗？是的，它是Rails 3.0.3项目。您可以使用类似gem的项目，或者两者都可以生成嵌套哈希。感谢支持，是否可以生成它而不在数据库中添加任何字段？闭包树使用

parent\u id

列，您只需设置一个附加表并运行rake任务，看到这两个gem真的很棒，我们能在没有任何数据库迁移的情况下完成吗？谢谢你的时间，对我来说理解build_tree背后的概念很复杂。

groups = arr.group_by{ |x| x[:parent_id] }
groups.default = []

build_tree = 
  lambda do |parent| 
    [parent[:title], groups[parent[:id]].map(&build_tree)]
    # or
    # { parent[:title] => groups[parent[:id]].map(&build_tree) }
  end

p build_tree[:id => nil][1] # :id => nil is not required, empty hash will work too
# => [["A", [["A1", [["A11", []], ["A12", [["A122", []]]]]], ["A2", [["A21", []]]]]], ["B", [["B11", []], ["B12", []]]]]

#!/usr/bin/env ruby

root = {:id => 0, :title => '', :parent_id => nil}

arr = arr = [
  {:id=>1,  :title=>"A",      :parent_id=>nil}, 
  {:id=>2,  :title=>"B",      :parent_id=>nil},
  {:id=>3,  :title=>"A1",     :parent_id=>1}, 
  {:id=>4,  :title=>"A2",     :parent_id=>1},
  {:id=>5,  :title=>"A11",    :parent_id=>3}, 
  {:id=>6,  :title=>"12",     :parent_id=>3},
  {:id=>7,  :title=>"A2=121", :parent_id=>6}, 
  {:id=>8,  :title=>"A21",    :parent_id=>4},
  {:id=>9,  :title=>"B11",    :parent_id=>2}, 
  {:id=>10, :title=>"B12",    :parent_id=>2},
]

map = {}

arr.each do |e|
  map[e[:id]] = e
end

@@tree = {}

arr.each do |e|
  pid = e[:parent_id]
  if pid == nil || !map.has_key?(pid)
    (@@tree[root] ||= []) << e
  else
    (@@tree[map[pid]] ||= []) << e
  end
end

def print_tree(item, level)
  items = @@tree[item]
  unless items == nil
    indent = level > 0 ? sprintf("%#{level * 2}s", " ") : ""
    items.each do |e|
      puts "#{indent}-#{e[:title]}"
      print_tree(e, level + 1)
    end
  end
end

print_tree(root, 0)

-A
  -A1
    -A11
    -12
      -A2=121
  -A2
    -A21
-B
  -B11
  -B12