如何在Ruby散列中计算特定值的外观数？

Question

我有一个Ruby哈希(最初是rails中的param )

如何计算每个correctness中的answers_attributes数？

(我这么做的原因是，我试图用rails创建一个多项选择的测试。一个问题可能有很多答案。我试图使用multi_correct复选框来决定哪个问题有许多正确的答案。但这有点违背直觉。因此，我希望后端通过计算每个问题的正确性来决定)

{
  "utf8" => "✓", "authenticity_token" => "r5xX46JG/GPF6+drEWmMPR+LpOI0jE0Tta/ABQ0rZJJE+UbbEjvNMLP6y2Z9IsWlXq27PR6Odx0EK4NECPjmzQ==", "question_bank" => {
    "name" => "123213", "questions_attributes" => {
      "0" => {
        "content" => "question 1", "multi_correct" => "no", "answers_attributes" => {
          "0" => {
            "content" => "as1", "correctness" => "false"
          }, "1" => {
            "content" => "as2", "correctness" => "false"
          }, "2" => {
            "content" => "as3", "correctness" => "true"
          }, "3" => {
            "content" => "as4", "correctness" => "false"
          }
        }
      }, "1" => {
        "content" => "q2", "multi_correct" => "no", "answers_attributes" => {
          "0" => {
            "content" => "a1", "correctness" => "false"
          }, "1" => {
            "content" => "a2", "correctness" => "false"
          }, "2" => {
            "content" => "a3", "correctness" => "true"
          }, "3" => {
            "content" => "a4", "correctness" => "false"
          }
        }
      }, "2" => {
        "content" => "q3", "multi_correct" => "no", "answers_attributes" => {
          "0" => {
            "content" => "aa1", "correctness" => "false"
          }, "1" => {
            "content" => "aa2", "correctness" => "false"
          }, "2" => {
            "content" => "aa3", "correctness" => "false"
          }, "3" => {
            "content" => "aa4", "correctness" => "true"
          }
        }
      }
    }
  }, "commit" => "Submit"
}

Answer 1

如果您只想计算散列中有多少正确的答案，可以使用inject来完成。以下是一种方法：

# iterate over the questions
hash['question_bank']['questions_attributes'].values.inject(0) do |count, q|
  # iterate over the answers
  count += q['answers_attributes'].values.inject(0) do |a_count, a|
    a_count += a['correctness'] == 'true' ? 1 : 0
  end
end