Question

编辑**
arr = [{＆＃34;番茄＆＃34; =＆gt; 2}，{＆＃34;香蕉＆＃34; =＆gt; 3}，{＆＃34;牛奶＆＃34; =＆gt; 1}，{＆＃34; egg＆＃34; =＆gt; 1}，{＆＃34;烹饪箔＆＃34; =＆gt; 1}，{＆＃34; apple＆＃34; =＆gt; 4}，{＆＃34; apple =→6}]

如何更改值{"apple" => 10}？

如何定义函数，例如add以在添加相同密钥时更新值？例如

arr.add{"banana" =>7}
=>
[{"tomato"=>2}, {"banana"=>10}, {"milk"=>"1 gallon"}, {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>10}]

Answer 1

您可以定义一个使用detect来查找给定密钥并对其进行编辑的函数。如果密钥尚未存在，还要添加新条目。类似的东西：

def add(key, val, arr)
  a = arr.detect{|a| a[key]}
  a ? a[key] = a[key] + val : arr << {key => val}
  arr
end

arr = [{"tomato"=>2}, {"banana"=>3}, {"milk"=>"1 gallon"}, {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>4}, {"apple" =>6}]

add("apple", 10, arr)
# => [{"tomato"=>2}, {"banana"=>3}, {"milk"=>"1 gallon"}, {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>14}, {"apple"=>6}]

add("banana", 6, arr)
# => [{"tomato"=>2}, {"banana"=>9}, {"milk"=>"1 gallon"}, {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>14}, {"apple"=>6}]

add("lemon", 3, arr)
# => [{"tomato"=>2}, {"banana"=>9}, {"milk"=>"1 gallon"}, {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>14}, {"apple"=>6}, {"lemon"=>3}]

注意：由于您的数组有两个具有相同键的哈希，detect将仅更改第一个匹配项。如果要替换所有哈希，可以使用find_all。

Answer 2

我假设所有以"apple"作为单个密钥的哈希值都将替换为单个哈希{ "apple"=>tot }，其中tot是"apple"的所有值的总和引用的哈希值中的{1}}。我还假设arr不会被更改，并且返回的数组中{"apple"=>tot}的位置并不重要。

arr = [{"tomato"=>2}, {"banana"=>3}, {"milk"=>"1 gallon"}, {"egg"=>"1 cart"},
       {"cooking foil"=>1}, {"apple"=>4}, {"apple"=>6}]

apples = arr.select { |h| h.keys.include?("apple") }
arr - apples << { "apple"=> apples.reduce(0) { |tot,h| tot + h["apple"] } }
  #=> [{"tomato"=>2}, {"banana"=>3}, {"milk"=>"1 gallon"},
  #    {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>10}]

步骤：

提取以"apple"作为单个键的哈希值（保持arr不变）：

apples = arr.select { |h| h.keys.include?("apple") }
  #=> [{"apple"=>4}, {"apple"=>6}]

计算苹果总数：

tot_apples = apples.reduce(0) { |tot,h| tot + h["apple"] }
  #=> 10

选择没有arr作为关键字的"apple"元素（保持arr不变）：

a = arr - apples
  #=> [{"tomato"=>2}, {"banana"=>3}, {"milk"=>"1 gallon"},
  #    {"egg"=>"1 cart"}, {"cooking foil"=>1}]

最后，将{ "apple"=>tot_apples }追加到a：

a << { "apple"=>tot_apples }
  #=> [{"tomato"=>2}, {"banana"=>3}, {"milk"=>"1 gallon"},
  #    {"egg"=>"1 cart"}, {"cooking foil"=>1}, {"apple"=>10}]

如何更新数组中的哈希值？

2 个答案: