Object 可能是 undefined formio onchange

Question

我有这个错误：

Error: src/app/app.component.html:1:30 - error TS2532: Object is possibly 'undefined'.

1 <form-builder [form]="form" (change)="onChange($event)"></form-builder>

在我的表单生成器中。 我认为是(change)问题。 但是老实说，我不知道为什么以及如何解决它

Answer 1

 import { Component, ElementRef, OnInit, ViewChild } from '@angular/core'; @Component({ selector: 'app-form-crear', templateUrl: './form-crear.component.html', styleUrls: ['./form-crear.component.scss'] }) export class FormCrearComponent implements OnInit { @ViewChild('json') jsonElement?: ElementRef | any; @ViewChild('formio') formio:any; public form: any = { components: [ ] }; ngOnInit(): void { } guardarFormulario(){ this.jsonElement.nativeElement.innerHTML = ''; this.jsonElement.nativeElement.appendChild(document.createTextNode(JSON.stringify(this.formio.form, null, 4))); const json = document.createTextNode(JSON.stringify(this.formio.form, null, 4)); } }

 <div class="container-fluid"> <div class="row"> <div class="col-12"> <form-builder [form]="form" #formio></form-builder> </div> </div> <hr class="linea"> <button (click)="guardarFormulario()">Ver formulario</button> <div class="well jsonviewer"> <pre id="json"><code class="language-json" #json></code></pre> </div> </div>