javascript - 无法在 Angular 6 中设置未定义的属性 'title'

Question

为什么我会收到此错误无法设置未定义的属性“标题”这是我的代码 https://stackblitz.com/edit/angular-pkd3qr?file=src%2Fapp%2Fapp.component.ts

import { Component } from '@angular/core';


interface DropDownModel {
  displayName: string;
  value: string;
}

interface DropdownModelWithtitle {
  title: string;
  dropDownOptions: DropDownModel[];
}

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  name = 'Angular';
  typeOfProofObj: DropdownModelWithtitle;
  constructor(){
    this.typeOfProofObj.title = "ss";
    this.typeOfProofObj.dropDownOptions = [{displayName:'ss',value:'sss'}];

  }

}

我正在尝试将值插入到我的变量中，那么如何解决此问题？

Answer 1

您需要首先初始化typeOfProofObj变量，然后尝试访问它的属性。

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  name = 'Angular';
  typeOfProofObj: DropdownModelWithtitle = { title: null, dropDownOptions: null };

  constructor() {
     this.typeOfProofObj.title = "ss";
     this.typeOfProofObj.dropDownOptions = [ {displayName: 'ss', value: 'sss'} ];    
  }

}