domains = [
  { "country" => "Germany"},{"country" => "United Kingdom"},{"country" => "Hungary"},{"country" => "United States"},{"country" => "France"},{"country" => "Germany"},{"country" => "Slovakia"},{"country" => "Norway"},{"country" => "Norway"}
]

从这个散列数组我想创建一个新的哈希看起来像这样：

counted = {
  "Germany" => "3","United Kingdom" => "United Kingdom","Hungary" => "3","United States" => "4","France" => "1"
}

有没有一个简单的方法来做这个使用Ruby 1.9？

解决方法

counted = Hash.new(0)
domains.each { |h| counted[h["country"]] += 1 }
counted = Hash[counted.map {|k,v| [k,v.to_s] }]

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