我有一个 Ruby 对象数组，如何根据这些对象的属性将此数组更改为多个数组？

Question

根据原始数组中对象的属性，将一个大数组变为多个子数组的最佳方法是什么？例如我有一个对象数组（所有对象都具有相同的属性）：

array = [
    {:name => "Jim", :amount => "20"},
    {:name => "Jim", :amount => "40"},
    {:name => "Jim", :amount => "30"},
    {:name => "Eddie", :amount => "7"},
    {:name => "Eddie", :amount => "12"},
    {:name => "Pony", :amount => "330"},
    {:name => "Pony", :amount => "220"},
    {:name => "Pony", :amount => "50"}
]

请注意，所有具有相同 name 属性的对象在数组中都是连续的。现在我想根据 name 属性将对象分组到子数组中。我需要的是：

result = [
    [
        {:name => "Jim", :amount => "20"},
        {:name => "Jim", :amount => "40"},
        {:name => "Jim", :amount => "30"}
    ],
    [
        {:name => "Eddie", :amount => "7"},
        {:name => "Eddie", :amount => "12"}
    ],
    [
        {:name => "Pony", :amount => "330"},
        {:name => "Pony", :amount => "220"},
        {:name => "Pony", :amount => "50"}
    ]
]

最好的方法是什么？ 谢谢。

Answer 1

使用group_by 进行繁重的工作，然后使用map 提取您想要的内容：

result = array.group_by { |h| h[:name] }.map { |k, v| v }

例如：

>> results = array.group_by { |h| h[:name] }.map { |k, v| v }
>> pp results
[[{:name=>"Jim", :amount=>"20"},
  {:name=>"Jim", :amount=>"40"},
  {:name=>"Jim", :amount=>"30"}],
 [{:name=>"Eddie", :amount=>"7"},
  {:name=>"Eddie", :amount=>"12"}],
 [{:name=>"Pony", :amount=>"330"},
  {:name=>"Pony", :amount=>"220"},
  {:name=>"Pony", :amount=>"50"}]]

您也可以跳过map，直接转到Hash#values：

result = array.group_by { |h| h[:name] }.values

感谢 KandadaBoggu 指出这一疏忽。

Answer 2

如果具有相同 :name 值的哈希始终是连续元素，您可以这样做：

result = array.each_with_object([]) do |e, memo|
  if memo.last && memo.last.last[:name] == e[:name]
    memo.last << e
  else
    memo << [e] 
  end 
end

或者您可以使用Enumerable#chunk（再次考虑到具有相同:name 值的元素是连续的）：

result = array.chunk{ |e| e[:name] }.map(&:last)