如何通过设置关键元素的优先级来使用字符串键对ruby哈希进行排序？

Question

我有一个包含以下值的哈希:

hash = {
  'red': { something: ''},
  'green': { something: '' },
  'yellow': { something: ''}
}

做这样的事情最简单的方法是什么:

hash.sort_by_key_with_priority(['green', 'yellow', 'red'])

并返回:

hash = {
  'green': { something: '' },
  'yellow': { something: ''},
  'red': { something: ''},
}

Answer 1

如果优先级数组包含所有哈希键,则不需要排序.您可以简单地将哈希分开并构建一个新哈希.

hash = {
  red: { something: ''},
  green: { something: '' },
  yellow: { something: ''}
}

priority = %i[green yellow red]

hash.slice(*priority)
# => {:green=>{:something=>""}, :yellow=>{:something=>""}, :red=>{:something=>""}}

Answer 2

如果哈希中的键未包含在优先级数组中：

>> h = {red: 512, green: 63, yellow: 99, foo: 42, baz: 'hi'}
=> {:red=>512, :green=>63, :yellow=>99, :foo=>42, :baz=>"hi"}
>> p = %i[green yellow red]
=> [:green, :yellow, :red]

# this puts keys not in array at start
# h.sort_by { |k, v| p.include?(k) ? p.index(k) : -1 }
>> h.sort_by { |k, v| p.index(k) || -1 }
=> [[:foo, 42], [:baz, "hi"], [:green, 63], [:yellow, 99], [:red, 512]]

# this puts keys not in array at end
# h.sort_by { |k, v| p.include?(k) ? p.index(k) : p.size }
>> h.sort_by { |k, v| p.index(k) || p.size }
=> [[:green, 63], [:yellow, 99], [:red, 512], [:foo, 42], [:baz, "hi"]]

对结果使用to_h方法来转换为hash