未定义的角度对象数组值引发错误

我正在研究Angular6应用程序。我有输入的行为变量,一旦我收到数据,我就映射到SurveyInfo对象。我有如下所示的SurveyInfoDataModel类;接下来我试图通过读取模板中的SurveyInfo对象来显示此数据,但出现错误

错误

ERROR TypeError: Cannot read property 'surveyId' of undefined

成分

export class MyComponent implements OnInit {

@Input() surveySelectedToGetInfo: BehaviorSubject<any>;

ngOnInit() {

this.surveySelectedToGetInfo.subscribe(surveyDataItem=>{
  debugger;
  if(surveyDataItem!=null){
    this.loadSurveyInformation(surveyDataItem);
  }
 });
}

 private loadSurveyInformation(selectedSurveyObject:any):any{
 var mappedObject = this.mapSurveyInfo(selectedSurveyObject);
}

 private mapSurveyInfo(survey:any):SurveyInfoDataModel{
 if(survey!=null){

  this.surveyInfo = new SurveyInfoDataModel(
    survey.consultationId,
    survey.surveyId,
    survey.surveyIdNum,
    survey.surveyName
  );  
 }
  return this.surveyInfo;
}

测量信息数据模型类

export class SurveyInfoDataModel{
    surveyId:string;
    surveyIdNum:string;
    surveyName:string;
    consultationId:string;

constructor(consultationId, surveyId, surveyIdNum, surveyName ){
    this.consultationId =consultationId;
    this.surveyId = surveyId;
    this.surveyIdNum = surveyIdNum;
    this.surveyName = surveyName;

 }
}

HTML模板

<div class="surveyListInfoBlock">
 <div *ngIf="surveyInfo">
   {{surveyInfo.surveyId}}
 </div>
</div>