Angular 在“角度”中，为嵌套对象指定值

我正在研究Angular 2应用程序。我有嵌套对象“子问题”的对象。我需要给它赋值，但无法识别作为子问题ID的错误。subQuestionId是子问题的属性

错误 数据类 组成部分

---

子问题

是尚未实例化的对象

您可以通过以下方式消除此错误：

answerData.subQuestions = { subQuestionId: subQuestionId };

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您得到的错误到底是什么？TypeError:无法设置未定义的属性'subQuestionId'

export class AnswerEntryDataModel{

consultationId:string;
responseId:string;
questionId:string;
answers:string[];
isPreDefineAnswer:boolean;
subQuestions:{
    subQuestionId:string;
    isPreDefineSubAnswer:boolean;
    subQuestionAnswers:string[];
 }
}

export class myComponent implements OnInit {

private answerData = new AnswerEntryDataModel();
private answersList:string [] = []; 
private subQuestionAnswersList:string [] = []; 

 private assembleAnswer( responseId:string, questionId:string, subQuestionId:string, subQuestionInputType:string, subQuestionAnswersList:string[] ):AnswerEntryDataModel
{

  this.answerData.answers = [];

  this.answerData.consultationId = this.session.getItem('consultationId');
  this.answerData.responseId = responseId;
  this.answerData.questionId = questionId;

  if(subQuestionId!=null || subQuestionId!="undefined")
  {

    answerData.subQuestions.subQuestionId = subQuestionId; //throw error from here

    if(subQuestionInputType =="textbox"){  
      this.answerData.subQuestions.isPreDefineSubAnswer = false;
    }
    else {
      this.answerData.subQuestions.isPreDefineSubAnswer = true;
    }

    if(subQuestionAnswersList.length>0)
    {
      for(var itemIndex in subQuestionAnswersList)
      {
        this.answerData.subQuestions.subQuestionAnswers.push(subQuestionAnswersList[itemIndex]);
      }
    }

  }

  console.log("***** complete answer data ", this.answerData);

  return this.answerData;

}

answerData.subQuestions = { subQuestionId: subQuestionId };