基于匹配键的Ruby组哈希，将不匹配键的值存储在数组中

Question

需要基于以下哈希值实现给定的输出

foos = [ { :key => 'Foo', :value => 1, :revenue => 2 },
         { :key => 'Foo', :value => 1, :revenue => 4 },
         { :key => 'Bar', :value => 2, :revenue => 7 },
         { :key => 'bar', :value => 2, :revenue => 9 },
         { :key => 'Zampa', :value => 4, :revenue => 9 }]

输出应为：

{ :key => 'Foo', :value => 1, :revenue => [2,4] } #Merging row 1 & 2 as they share same :key 'Foo'
{ :key => 'Bar', :value => 2, :revenue => [7,9] } #Merging row 3 & 4 as they share same :key 'Bar'
{ :key => 'Zampa', :value => 4, :revenue => 9 } 

合并应基于：Key字段的值我是红宝石新手，如何在红宝石中实现这一目标。

Answer 1

您可以尝试按key和value分组，然后映射revenue值：

foos
  .group_by { |e| e.values_at(:key, :value) }
  .map do |(key, value), values|
    { key: key, value: value, revenue: values.map { |e| e[:revenue] } }
  end
# [{:key=>"Foo", :value=>1, :revenue=>[2, 4]}, {:key=>"Bar", :value=>2, :revenue=>[7]}, {:key=>"bar", :value=>2, :revenue=>[9]}, {:key=>"Zampa", :value=>4, :revenue=>[9]}]

Answer 2

使用减少

result=foos.group_by { |x| x[:key] }.values.map do |arr|
  arr.reduce do |h1, h2|
    h1.merge(h2) do |k, v1, v2|
      k.eql?(:revenue) ? [v1, v2] : v1
    end
  end
end

p结果

[{:key=>"Foo", :value=>1, :revenue=>[2, 4]}, {:key=>"bar", :value=>2, :revenue=>[7, 9]}, {:key=>"Zampa", :value=>4, :revenue=>9}]

Answer 3

您可以使用group_by将group_by阵列按foos分组。但是，我想先将:key值设为downcase，因为您希望downcase和:key结束于同一组。

'Bar'

结合以上步骤，我们得到以下结果：

'bar'

如果您不想修改原始的

# We first need to unify the keys of the hashes before we can start
# grouping. 'Foo' != 'foo' so they would be split up in two separate
# groups. Judging from the output you don't want this.
foos.each { |foo| foo[:key].downcase! }

# Now that all keys are downcased we can group based upon the value of
# the :key key.
grouped_foos = foos.group_by { |foo| foo[:key] }

# Now we need to map over the resulting hash and create a single result
# for each group.
grouped_foos.transform_values! do |foos|
  # First I'll transform the structure of `foos`, from:
  #
  #     [{a: 1, b: 2}, {a: 3, b: 4}]
  #
  # into:
  #
  #     [[:a, 1], [:b, 2], [:a, 3], [:b, 4]]
  #
  tmp = foos.flat_map(&:to_a)

  # Then I'll group the above structure based upon the first value in
  # each array, simultaneously removing the first element. Resulting in:
  #
  #     {a: [[1], [3]], b: [[2], [4]]}
  #
  tmp = tmp.group_by(&:shift)

  # We now need to flatten the values by one level. Resulting in:
  #
  #     {a: [1, 3], b: [2, 4]}
  #
  tmp.transform_values! { |values| values.flatten(1) }

  # The next step is remove duplicate values. We currently have:
  #
  #     {key: ['foo', 'foo'], value: [1, 1], revenue: [2, 4]}
  #
  # whereas we want:
  #
  #     {key: ['foo'], value: [1], revenue: [2, 4]}
  #
  tmp.transform_values!(&:uniq)

  # Lastly if the array only contains a single value we want to use the
  # value instead of an array. Transforming the above structure into:
  #
  #     {key: 'foo', value: 1, revenue: [2, 4]}
  #
  tmp.transform_values! { |head, *tail| tail.empty? ? head : [head, *tail] }

  # Finally we need to return our new hash.
  tmp 
end

结构，则必须替换：

foos.each { |foo| foo[:key].downcase! }
grouped_foos = foos.group_by { |foo| foo[:key] }

grouped_foos.transform_values! do |foos|
  foos.flat_map(&:to_a).group_by(&:shift)
      .transform_values { |values| values.flatten(1).uniq }
      .transform_values { |head, *tail| tail.empty? ? head : [head, *tail] }
end

然后从那时开始使用新的foos结构。

以上解决方案产生以下结果：

foos.each { |foo| foo[:key].downcase! }
# with
unified_keys = foos.map(&:dup).each { |foo| foo[:key] = foo[:key].downcase }

您可以通过请求unified_keys的值来获得所需的结果：

grouped_foos
#=> {"foo"  =>{:key=>"foo",   :value=>1, :revenue=>[2, 4]},
#    "bar"  =>{:key=>"bar",   :value=>2, :revenue=>[7, 9]},
#    "zampa"=>{:key=>"zampa", :value=>4, :revenue=>9}}