ruby-on-rails - 用散列对数组求和

Question

如何在这两个哈希数组之间执行加法，例如我想从第一个数组中获取第一个哈希并将 number, s_number, l_number 与第二个数组中的第一个哈希相加数组，总和将取决于 created_at，如果第一个数组中的 created_at 与第二个数组中的 created_at 相等，则执行 +。请查看我希望返回的内容，因为我不知道如何更好地解释这一点。

谢谢

raw_data = [
        [
            {"created_at"=>"2013-11-17","number"=>0,"s_number"=>0,"l_number"=>0},
            {"created_at"=>"2013-11-18","number"=>6,"s_number"=>1,"l_number"=>4},
            {"created_at"=>"2013-11-19","number"=>1,"s_number"=>1,"l_number"=>1},
            {"created_at"=>"2013-11-20","number"=>0,"s_number"=>0,"l_number"=>0}
        ],
        [
            {"created_at"=>"2013-11-17","number"=>2,"s_number"=>3,"l_number"=>4},
            {"created_at"=>"2013-11-18","number"=>1,"s_number"=>41,"l_number"=>1},
            {"created_at"=>"2013-11-19","number"=>5,"s_number"=>45,"l_number"=>7},
            {"created_at"=>"2013-11-20","number"=>7,"s_number"=>8,"l_number"=>2}    
        ]
        ]

应该返回什么

[
        {"created_at"=>"2013-11-17","number"=>2,"s_number"=>3,"l_number"=>4},
        {"created_at"=>"2013-11-18","number"=>7,"s_number"=>42,"l_number"=>5},
        {"created_at"=>"2013-11-19","number"=>6,"s_number"=>46"l_number"=>8},
        {"created_at"=>"2013-11-20","number"=>7,"s_number"=>8,"l_number"=>2}    
]

更新哈希格式与我发布的不同:

{:created_at=>Sun, 17 Nov 2013, :number=>0, :s_number=>0, :l_number=>0}

Answer 1

首先你需要对数组求和:

raw_data.sum

这将返回如下内容:

    [
        {"created_at"=>"2013-11-17","number"=>0,"s_number"=>0,"l_number"=>0},
        {"created_at"=>"2013-11-18","number"=>6,"s_number"=>1,"l_number"=>4},
        {"created_at"=>"2013-11-19","number"=>1,"s_number"=>1,"l_number"=>1},
        {"created_at"=>"2013-11-20","number"=>0,"s_number"=>0,"l_number"=>0}
        {"created_at"=>"2013-11-17","number"=>2,"s_number"=>3,"l_number"=>4},
        {"created_at"=>"2013-11-18","number"=>1,"s_number"=>41,"l_number"=>1},
        {"created_at"=>"2013-11-19","number"=>5,"s_number"=>45,"l_number"=>7},
        {"created_at"=>"2013-11-20","number"=>7,"s_number"=>8,"l_number"=>2}    
    ]

现在，我们需要按“created_at”键对元素进行分组:

raw_data.sum.group_by{|element| element['created_at']}

这将导致:

{
    "2013-11-17" => [
        {"created_at"=>"2013-11-17","number"=>0,"s_number"=>0,"l_number"=>0},
        {"created_at"=>"2013-11-17","number"=>2,"s_number"=>3,"l_number"=>4},
      ],
    "2013-11-18" => [
        {"created_at"=>"2013-11-18","number"=>6,"s_number"=>1,"l_number"=>4},
        {"created_at"=>"2013-11-18","number"=>1,"s_number"=>41,"l_number"=>1}
      ], ...           
}

我们只需要这个散列的值:

raw_data.sum.group_by{|element| element['created_at']}.values

# =>
    [
      [
        {"created_at"=>"2013-11-17","number"=>0,"s_number"=>0,"l_number"=>0},
        {"created_at"=>"2013-11-17","number"=>2,"s_number"=>3,"l_number"=>4},
      ],
      [
        {"created_at"=>"2013-11-18","number"=>6,"s_number"=>1,"l_number"=>4},
        {"created_at"=>"2013-11-18","number"=>1,"s_number"=>41,"l_number"=>1}
      ], ...           
}

现在我们需要将每个散列数组映射到一个散列。为此，我们将使用带有 block 的注入(inject)和合并功能:

raw_data.sum.group_by{|element| element[:created_at]}.values.map{|a| a.inject({}) {|result, hash| result.merge(hash) {|key, old_value, new_value| key == :created_at ? old_value : old_value + new_value}}}



# =>

[
    {"created_at"=>"2013-11-17","number"=>2,"s_number"=>3,"l_number"=>4},
    {"created_at"=>"2013-11-18","number"=>7,"s_number"=>42,"l_number"=>5},
    {"created_at"=>"2013-11-19","number"=>6,"s_number"=>46"l_number"=>8},
    {"created_at"=>"2013-11-20","number"=>7,"s_number"=>8,"l_number"=>2}    
]