为类似的 AR 查询实现查询对象的正确方法

Question

我的 rails 应用程序模型中有两种方法。

def questions_mastered_for(user_id, question_group_ids)
  res = UserAnswer
          .joins('INNER JOIN question_group_questions ON user_answers.question_id = question_group_questions.question_id')
          .joins('INNER JOIN marks ON user_answers.id = marks.user_answer_id')
          .group('question_group_questions.question_group_id')
          .where(question_group_questions: { question_group_id: question_group_ids })
          .where(user_answers: { user_id: user_id })
          .where("(marks.boolean_mark_correct = true AND marks.mark_type = 'boolean') OR (marks.fraction_numerator = marks.fraction_denominator AND marks.mark_type = 'fraction')")
          .pluck('question_group_questions.question_group_id', 'COUNT(DISTINCT(user_answers.question_id))')
  question_group_mastery = {}
  question_group_ids.each { |question_group_id| question_group_mastery[question_group_id] = 0 }
  res.each { |data| question_group_mastery[data.first] = data.second }
  question_group_mastery
end
def questions_attempted_for(user_id, question_group_ids)
  res = UserAnswer
          .joins('INNER JOIN question_group_questions ON user_answers.question_id = question_group_questions.question_id')
          .group('question_group_questions.question_group_id')
          .where(question_group_questions: { question_group_id: question_group_ids })
          .where(user_answers: { user_id: user_id })
          .pluck('question_group_questions.question_group_id', 'COUNT(DISTINCT(user_answers.question_id))')
  question_group_attempted = {}
  question_group_ids.each { |question_group_id| question_group_attempted[question_group_id] = 0 }
  res.each { |data| question_group_attempted[data.first] = data.second }
  question_group_attempted
end

如果我们可以从上面的方法中看到，两者都执行几乎相似的查询，唯一的区别是questions_mastered_for有额外的连接和 where 条件marks表。

我读了一些文章，说这个特定的用例通常可以使用查询对象来解决，但我想知道如何正确实现它？

任何建议我都非常感谢。

Answer 1

def questions_attempted_for_query(user_id, question_group_ids)
  UserAnswer
          .joins('INNER JOIN question_group_questions ON user_answers.question_id = question_group_questions.question_id')
          .group('question_group_questions.question_group_id')
          .where(question_group_questions: { question_group_id: question_group_ids })
          .where(user_answers: { user_id: user_id })
end
def questions_mastered_for(user_id, question_group_ids)
  res = questions_attempted_for_query(user_id, question_group_ids)
          .joins('INNER JOIN marks ON user_answers.id = marks.user_answer_id')
          .where("(marks.boolean_mark_correct = true AND marks.mark_type = 'boolean') OR (marks.fraction_numerator = marks.fraction_denominator AND marks.mark_type = 'fraction')")
          .pluck('question_group_questions.question_group_id', 'COUNT(DISTINCT(user_answers.question_id))')
  question_group_mastery = {}
  question_group_ids.each { |question_group_id| question_group_mastery[question_group_id] = 0 }
  res.each { |data| question_group_mastery[data.first] = data.second }
  question_group_mastery
end
def questions_attempted_for(user_id, question_group_ids)
  res = questions_attempted_for_query(user_id, question_group_ids)
          .pluck('question_group_questions.question_group_id', 'COUNT(DISTINCT(user_answers.question_id))')
  question_group_attempted = {}
  question_group_ids.each { |question_group_id| question_group_attempted[question_group_id] = 0 }
  res.each { |data| question_group_attempted[data.first] = data.second }
  question_group_attempted
end