Question

在这里，我试图创建一个使用MVC模式从数据库检索一些数据的函数。

查看

getQuestionsData (treatmentId) {

  console.log(1)

  controller.getTreatmentQuestions(treatmentId)
    .then(questions => {

      console.log(10)

      this.questions = questions   // variable is updated
    })
},

控制器

getTreatmentQuestions: async (treatmentTypeId) => {

  console.log(2)

  // first data fetch from db
  const questions = await model.getQuestion(treatmentTypeId)

  console.log(3)

  // iterate over each result record
  questions.map(async question => {

    console.log(4)

    if (question.answerType === 'select') {

      console.log(5)

      // second data fetch from db
      const answerWithChoices = await model.getQuestionChoices(question.id)

      console.log(9)

      // update question object with fetched data
      question = Object.assign({}, question, {
        choices: answerWithChoices.choices
      })
    }

    return question
  })

  return questions
}

模型

static async getQuestionChoices (questionId) {
  console.log(6)
  const answers = await db.choiceAnswers
    .where('questionId').equals(intId)
    .with({
      selectChoices: 'choiceAnswersChoices'
    })

  console.log(7)

  return answers.map(answer => {

    console.log(8)

    answer.choices = answer.selectChoices

    return answer
  })
}

我确实希望在控制台中按以下顺序读取数字：1、2、3、4、5、6、7、8、9、10。而是在控制台中打印的顺序是：1、2、3、4、5、6、10、7、8、9。

这意味着模型的函数“ getQuestionChoices”不在等待return语句。

我该如何解决？

谢谢

Answer 1

此：

 questions.map(async question => {

    console.log(4)

    if (question.answerType === 'select') {

      console.log(5)

      // second data fetch from db
      const answerWithChoices = await model.getQuestionChoices(question.id)

      console.log(9)

      // update question object with fetched data
      question = Object.assign({}, question, {
        choices: answerWithChoices.choices
      })
    }

    return question
  })

返回一个promise数组，结果未分配到任何地方

解决方法：

 questions = await Promise.all(questions.map(async question => {

    console.log(4)

    if (question.answerType === 'select') {

      console.log(5)

      // second data fetch from db
      const answerWithChoices = await model.getQuestionChoices(question.id)

      console.log(9)

      // update question object with fetched data
      question = Object.assign({}, question, {
        choices: answerWithChoices.choices
      })
    }

    return question
  }))

异步/等待功能未等待

1 个答案: