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arrays - 如何将哈希数组与匹配的列值合并

问题描述

我想合并两个数组array1并array2匹配一个列值。两个数组之间的绘图 ID 可能匹配也可能不匹配。匹配列是 array1 中的绘图 ID 和 array2 中的绘图 ID。

主要是array1。array1 中的列值应首先出现在预期输出中。

如果 array2 与 array1 不匹配，则使用零值合并 array2 列名

array1 = [
{"Date" => "2019-01-01", "Plot ID" => 234},
{"Date" => "2019-01-01", "Plot ID" => 235},
{"Date" => "2019-01-01", "Plot ID" => 236},
{"Date" => "2019-01-01", "Plot ID" => 237},
{"Date" => "2019-01-01", "Plot ID" => 238},
{"Date" => "2019-01-01", "Plot ID" => 239},
{"Date" => "2019-01-01", "Plot ID" => 240},
{"Date" => "2019-01-01", "Plot ID" => 241}
]

array2 = [
{"Date" => "2019-01-01", "Plotting ID" => 234, "size"=> 20, "visit" => 10, "price" => 103},
{"Date" => "2019-01-01", "Plotting ID" => 500,  "size"=> 40, "visit" => 22, "price" => 233},
{"Date" => "2019-01-01", "Plotting ID" => 236,  "size"=> 25, "visit" => 34, "price" => 423},
{"Date" => "2019-01-01", "Plotting ID" => 600,  "size"=> 79, "visit" => 55, "price" => 234}
]

预期输出：

[
{"Date" => "2019-01-01", "Plot ID" => 234, "size"=> 20, "visit" => 10, "price" => 103},
{"Date" => "2019-01-01", "Plot ID" => 235, "size"=> 0, "visit" => 0, "price" => 0},
{"Date" => "2019-01-01", "Plot ID" => 236, "size"=> 25, "visit" => 34, "price" => 423},
{"Date" => "2019-01-01", "Plot ID" => 237, "size"=> 0, "visit" => 0, "price" => 0},
{"Date" => "2019-01-01", "Plot ID" => 238, "size"=> 0, "visit" => 0, "price" => 0},
{"Date" => "2019-01-01", "Plot ID" => 239, "size"=> 0, "visit" => 0, "price" => 0},
{"Date" => "2019-01-01", "Plot ID" => 240, "size"=> 0, "visit" => 0, "price" => 0},
{"Date" => "2019-01-01", "Plot ID" => 241, "size"=> 0, "visit" => 0, "price" => 0}
]

标签： arraysrubyhashmerge

解决方案

此答案仅在array2不包含任何重复Plotting ID值的情况下才有效。（如果有重复Plotting ID，它仍然有效，但它使用数组中曾经存在的最后一条记录。）

array1 = [{"Date" => "2019-01-01", "Plot ID" => 234}, {"Date" => "2019-01-01", "Plot ID" => 235}, {"Date" => "2019-01-01", "Plot ID" => 236}, {"Date" => "2019-01-01", "Plot ID" => 237}, {"Date" => "2019-01-01", "Plot ID" => 238}, {"Date" => "2019-01-01", "Plot ID" => 239}, {"Date" => "2019-01-01", "Plot ID" => 240}, {"Date" => "2019-01-01", "Plot ID" => 241}]
array2 = [{"Date" => "2019-01-01", "Plotting ID" => 234, "size"=> 20, "visit" => 10, "price" => 103}, {"Date" => "2019-01-01", "Plotting ID" => 500,  "size"=> 40, "visit" => 22, "price" => 233}, {"Date" => "2019-01-01", "Plotting ID" => 236,  "size"=> 25, "visit" => 34, "price" => 423}, {"Date" => "2019-01-01", "Plotting ID" => 600,  "size"=> 79, "visit" => 55, "price" => 234}]

array2_lookup = array2.map(&:dup).map { |record| [record.delete('Plotting ID'), record] }.to_h
array2_lookup.default = { 'size' => 0, 'visit' => 0, 'price' => 0 }
pp array1.map { |record| array2_lookup[record['Plot ID']].merge(record) }
# [{"Date"=>"2019-01-01", "size"=>20, "visit"=>10, "price"=>103, "Plot ID"=>234},
#  {"size"=>0, "visit"=>0, "price"=>0, "Date"=>"2019-01-01", "Plot ID"=>235},
#  {"Date"=>"2019-01-01", "size"=>25, "visit"=>34, "price"=>423, "Plot ID"=>236},
#  {"size"=>0, "visit"=>0, "price"=>0, "Date"=>"2019-01-01", "Plot ID"=>237},
#  {"size"=>0, "visit"=>0, "price"=>0, "Date"=>"2019-01-01", "Plot ID"=>238},
#  {"size"=>0, "visit"=>0, "price"=>0, "Date"=>"2019-01-01", "Plot ID"=>239},
#  {"size"=>0, "visit"=>0, "price"=>0, "Date"=>"2019-01-01", "Plot ID"=>240},
#  {"size"=>0, "visit"=>0, "price"=>0, "Date"=>"2019-01-01", "Plot ID"=>241}]

上述解决方案首先循环array2并将其转换为散列，方法是'Plotting ID'从散列中删除键/值对并将值用作键。出于这个原因，我添加了.map(&:dup)调用，以防止原始哈希值发生array2变异。如果散列突变对您来说不是问题，您可以简单地删除它。

创建查找哈希后，我添加了一个在合并哈希时使用的默认值。现在剩下要做的就是循环array1，查找记录（如果有的话）或使用默认值并将其与当前元素合并。

这个答案使键有些混乱，但是由于哈希无论如何都是基于键查找（不是键/值顺序），所以这应该不是一个大问题。如果您希望所有键的顺序相同，您可以通过将所有键提供为默认值，将它们的值设置为nil（或任何其他值，因为它们被覆盖）：

array2_lookup.default = { 'Date' => nil, 'size' => 0, 'visit' => 0, 'price' => 0 }
# ...                        ^ added placeholder for ordering purposes
# [{"Date"=>"2019-01-01", "size"=>20, "visit"=>10, "price"=>103, "Plot ID"=>234},
#  {"Date"=>"2019-01-01", "size"=>0, "visit"=>0, "price"=>0, "Plot ID"=>235},
#  {"Date"=>"2019-01-01", "size"=>25, "visit"=>34, "price"=>423, "Plot ID"=>236},
#  {"Date"=>"2019-01-01", "size"=>0, "visit"=>0, "price"=>0, "Plot ID"=>237},
#  {"Date"=>"2019-01-01", "size"=>0, "visit"=>0, "price"=>0, "Plot ID"=>238},
#  {"Date"=>"2019-01-01", "size"=>0, "visit"=>0, "price"=>0, "Plot ID"=>239},
#  {"Date"=>"2019-01-01", "size"=>0, "visit"=>0, "price"=>0, "Plot ID"=>240},
#  {"Date"=>"2019-01-01", "size"=>0, "visit"=>0, "price"=>0, "Plot ID"=>241}]

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