Ruby：如何按特定键的给定顺序对哈希数组进行排序

Question

我有一个哈希数组，其中id是哈希中的关键字之一。我想根据给定的ID值顺序对数组元素进行排序。

假设我的数组（大小=5）如下：

[{"id"=>1. ...}, {"id"=>4. ...}, {"id"=>9. ...}, {"id"=>2. ...}, {"id"=>7. ...}]

我希望对数组元素进行排序，按照它们的id顺序排列，顺序如下：

[1,3,5,7,9,2,4,6,8,10]

所以预期的结果是：

[{'id' => 1},{'id' => 7},{'id' => 9},{'id' => 2},{'id' => 4}]

- nish

Answer 1

以下是任何自定义索引的解决方案：

def my_index x 
  # Custom code can be added here to handle items not in the index.
  # Currently an error will be raised if item is not part of the index.
  [1,3,5,7,9,2,4,6,8,10].index(x) 
end

my_collection = [{"id"=>1}, {"id"=>4}, {"id"=>9}, {"id"=>2}, {"id"=>7}]
p my_collection.sort_by{|x| my_index x['id'] } #=> [{"id"=>1}, {"id"=>7}, {"id"=>9}, {"id"=>2}, {"id"=>4}]

然后你可以以任何你想要的方式进行格式化，也许这样更美观：

my_index = [1,3,5,7,9,2,4,6,8,10]
my_collection.sort_by{|x| my_index.index x['id'] }

- hirolau

Answer 2

一般的排序说明。使用Ruby的Array类的#sort_by方法：

[{'id' => 1},{'id'=>3},{'id'=>2}].sort_by {|x|x['id'] }
# => [{"id"=>1}, {"id"=>2}, {"id"=>3}]

或者使用 #values 方法作为回调函数：

[{'id' => 1},{'id'=>3},{'id'=>2}].sort_by(&:values)
# => [{"id"=>1}, {"id"=>2}, {"id"=>3}]

或者您可以使用更明显的版本，使用#sort方法：

[{'id' => 1},{'id'=>3},{'id'=>2}].sort {|x,y| x['id'] <=> y['id'] }
# => [{"id"=>1}, {"id"=>2}, {"id"=>3}]

对于您的情况，如果要按照扩展条件排序，请使用#%来区分偶数和奇数索引：

[{'id' => 1},{'id'=>4},{'id'=>9},{'id'=>2},{'id'=>7}].sort do |x,y|
    u = y['id'] % 2 <=> x['id'] % 2
    u == 0 && y['id'] <=> x['id'] || u 
end
# => [{"id"=>1}, {"id"=>7}, {"id"=>9}, {"id"=>2}, {"id"=>4}]

针对您的情况，要按扩展条件进行排序，请使用#%根据索引进行拆分，即使在索引数组中缺少id值也可以这样做。

index = [1,3,5,7,4,2,6,8,10] # swapped 2 and 4, 9 is absent

[{'id' => 1},{'id'=>4},{'id'=>9},{'id'=>2},{'id'=>7}].sort do |x,y|
   !index.rindex( x[ 'id' ] ) && 1 || index.rindex( x[ 'id' ] ) <=> index.rindex( y[ 'id' ] ) || -1 
end
# => [{"id"=>1}, {"id"=>7}, {"id"=>4}, {"id"=>2}, {"id"=>9}]

- Малъ Скрылевъ

---

预期结果是 [{'id' => 1},{'id' => 7},{'id' => 9},{'id' => 2},{'id' => 4}]。 - nish

@Малъ 我喜欢简洁的解决方案。 - Roman Kiselenko

@МалъСкрылевъ 这在这种情况下（先奇数再偶数）可以工作，但是否有一般解决方案。我可能会遇到希望顺序是随机的情况。 - nish

@МалъСкрылевъ：例如，所需顺序为[1,5,3,2,8,9,7,6,4]。 - nish

所以，请看一下我的答案，我已经回答了这个问题。 - hirolau

@hirolau：是的，我尝试了你的解决方案，它起作用了。抱歉我忘记接受答案。感谢你的帮助 :) - nish

Answer 3

我会像这样根据值来映射哈希表：

a = [{"id"=>1}, {"id"=>4}, {"id"=>9}, {"id"=>2}, {"id"=>7}]

[1,3,5,7,9,2,4,6,8,10].map{|x| a[a.index({"id" => x})] }.compact

#=> [{"id"=>1}, {"id"=>7}, {"id"=>9}, {"id"=>2}, {"id"=>4}]

- benjaminjosephw

Answer 4

a= [{"id"=>1}, {"id"=>4}, {"id"=>9}, {"id"=>2}, {"id"=>7}]
b=[1,3,5,7,9,2,4,6,8,10]
a.sort_by{|x| b.index (x['id'])}

- bluexuemei

Answer 5

为什么不直接使用sort呢？

def doit(arr, order)
  arr.sort { |h1,h2| order.index(h1['id']) <=> order.index(h2['id']) }
end

order = [1,3,5,7,9,2,4,6,8,10]
arr = [{'id' => 1}, {'id' => 4}, {'id' => 9}, {'id' => 2}, {'id' => 7}]     

doit(arr, order)
  #=> [{'id' => 1}, {'id' => 7}, {'id' => 9}, {'id' => 2}, {'id' => 4}]     

- Cary Swoveland