如何在嵌套數組/哈希上使用ruby uniq

Question

我正在嘗試在follow json上調用uniq方法，以使其僅返回基於employee_id的唯一結果

# Json array
a ={
  results: [
   {
    employee: {
      name: "A",
      employee_id: "A-00016",
      title: 1
     }
   },{
    employee: {
      name: "A",
      employee_id: "A-00016",
      title: 2
     }
   },{
    employee: {
      name: "C",
      employee_id: "C-00017",
      title: 3
     }
    }
   ]
  }



# Calling uniq on a
a.uniq { |p| p.values_at(:employee_id) }

但是，我只得到這個結果

{
  results: [
   {
    employee: {
      name: "A",
      employee_id: "A-00016",
      title: 1
     }
    }
   ]
  }

而不是我想要的

{
  results: [
   {
    employee: {
      name: "A",
      employee_id: "A-00016",
      title: 1
     },{
    employee: {
      name: "C",
      employee_id: "C-00017",
      title: 3
     }
    }
   ]
  }

我是否使用正確的方法輸出所需的結果？

Answer 1

與uniq ：

input[:results].uniq { |e| e[:employee][:employee_id] }
#⇒ [
#    {:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>"1"}},
#    {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>"3"}}]

但是我認為應該從具有相同id兄弟姐妹中選擇什么條件。 下面的代碼選擇一個具有最大title值的代碼：

input[:results].group_by { |e| e[:employee][:employee_id] }
               .map { |_, v| v.max_by { |e| e[:employee][:title].to_i } }
#⇒ [
#    {:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>"2"}},
#    {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>"3"}}]

Answer 2

這是一種方法，為了返回修改后的輸入hash ，我們可以使用uniq! 這將修改數組a[:results]到位。 我們使用dup復制哈希a來保留它，然后使用tap來處理重復的哈希。

r = a.dup.tap do |h|
  h[:results].uniq! do |h|
    h[:employee][:employee_id]
  end
end

#=> {:results=>
#    [
#     {:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>1}},
#     {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}
#    ]
#   }

Answer 3

def selection_criterion(h)
  h[:title].to_i
end

{results: a[:results].group_by {|h| h[:employee][:employee_id]}.
                      values.
                      map {|arr| arr.max_by {|h|  selection_criterion(h[:employee])}}}
   #=> {:results=>
   #     [{:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>2}},
   #      {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}]}        

根據需要定義selection_criterion ，並可能將max_by更改為min_by 。

步驟如下。

 b = a[:results]
   # => [{:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>1}},
   #     {:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>2}},
   #     {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}] 
 c = b.group_by { |h| h[:employee][:employee_id] }
   #=> {"A-00016"=>[{:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>1}},
   #                {:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>2}}],
   #    "C-00017"=>[{:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}]}
 d = c.values
   #=> [[{:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>1}},
   #     {:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>2}}],
   #    [{:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}]] 
 e = d.map { |arr| arr.max_by { |h| selection_criterion(h[:employee]) } }
   #=> [{:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>2}},
   #    {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}]
 { results: e }
   #=> {:results=>
   #     [{:employee=>{:name=>"A", :employee_id=>"A-00016", :title=>2}},
   #      {:employee=>{:name=>"C", :employee_id=>"C-00017", :title=>3}}]}