19

我有一个数组，它由 MongoDB 执行的 map/reduce 方法输出，它看起来像这样：

[{"minute"=>30.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>0.0, "count"=>299.0}, 
{"minute"=>30.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>10.0, "count"=>244.0}, 
{"minute"=>30.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>1.0, "count"=>204.0}, 
{"minute"=>45.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>0.0, "count"=>510.0}, 
{"minute"=>45.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>10.0, "count"=>437.0}, 
{"minute"=>0.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>0.0, "count"=>469.0}, 
{"minute"=>0.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>10.0, "count"=>477.0}, 
{"minute"=>15.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>0.0, "count"=>481.0}, 
{"minute"=>15.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>10.0, "count"=>401.0}, 
{"minute"=>30.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>0.0, "count"=>468.0}, 
{"minute"=>30.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>10.0, "count"=>448.0}, 
{"minute"=>45.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>0.0, "count"=>485.0}, 
{"minute"=>45.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "type"=>10.0, "count"=>518.0}]

您会注意到 有 3 个不同的值type，在这种情况下0、1和2，现在要做的是按其type键的值对这个哈希数组进行分组，因此例如这个数组最终看起来像：

{
  :type_0 => [
    {"minute"=>30.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>299.0}, 
    {"minute"=>45.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>510.0}, 
    {"minute"=>0.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>469.0}, 
    {"minute"=>15.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>481.0}, 
    {"minute"=>30.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>468.0}, 
    {"minute"=>45.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>485.0}
  ],

  :type_1 => [
    {"minute"=>30.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>204.0}
  ],

  :type_10 => [
    {"minute"=>30.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>244.0}, 
    {"minute"=>45.0, "hour"=>15.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>437.0},
    {"minute"=>0.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>477.0}, 
    {"minute"=>15.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>401.0}, 
    {"minute"=>30.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>448.0}, 
    {"minute"=>45.0, "hour"=>16.0, "date"=>5.0, "month"=>9.0, "year"=>2011.0, "count"=>518.0}
  ]
}

所以我知道这些示例数组非常大，但我认为这可能是一个比我想象的更简单的问题

因此，基本上每个哈希数组都将按其type键的值进行分组，然后作为带有每种类型数组的哈希返回，任何帮助都会非常有帮助，即使只是一些有用的提示也会非常感激。

4

4 回答 4

36 
array.group_by {|x| x['type']}

或者如果你想要符号键的东西，你甚至可以

array.group_by {|x| "type_#{x['type']}".to_sym}

我认为这最好地表达了“所以基本上每个散列数组都将按其类型 key 的值分组，然后作为带有每个类型数组的散列返回”，即使它:type在输出散列中单独留下键。

于 2011-10-06T03:44:51.750 回答
2 
by_type = {}

a.each do |h|
   type = h.delete("type").to_s
   # type = ("type_" + type ).to_sym

   by_type[ type ] ||= []
   by_type[ type ] << h      # note: h is modified, without "type" key

end

注意：这里的哈希键略有不同，我直接使用类型值作为键

如果您必须拥有示例中的哈希键，则可以添加被注释掉的行。

PS：我刚刚看到了 Tapio 的解决方案——它非常好而且很短！请注意，它仅适用于 Ruby >= 1.9

于 2011-10-06T03:34:34.380 回答
2

大概是这样的？

mangled = a.group_by { |h| h['type'].to_i }.each_with_object({ }) do |(k,v), memo|
    tk = ('type_' + k.to_s).to_sym
    memo[tk] = v.map { |h| h = h.dup; h.delete('type'); h }
end

或者，如果您不关心保留原始数据：

mangled = a.group_by { |h| h['type'].to_i }.each_with_object({ }) do |(k,v), memo|
    tk = ('type_' + k.to_s).to_sym
    memo[tk] = v.map { |h| h.delete('type'); h } # Drop the h.dup in here
end
于 2011-10-06T03:39:25.730 回答
2

group_by 将可枚举对象收集到集合中，并按块的结果分组。您不限于简单地获取此块中的键值，因此如果您想省略'type'这些集合中的 ，您可以这样做，例如：

array.group_by {|x| "type_#{x.delete('type').to_i}".to_sym}

这将完全符合您的要求。

高级：这有点超出了问题的范围，但是如果要保留原始数组，则必须复制其中的每个对象。这可以解决问题：

array.map(&:dup).group_by {|x| "type_#{x.delete('type').to_i}".to_sym}
于 2015-09-03T11:19:50.163 回答