javascript - 未捕获的类型错误 : Cannot read property 'element' of undefined when press login button

Question

我收到此错误

Uncaught TypeError: Cannot read property 'element' of undefined

当我按下 ionic2 和 angular2 应用程序中的登录按钮时。 我试图查看未初始化或未运行的变量，但我根本没有找到。

这就是登录功能

import { Component } from '@angular/core';
import { NavController,ViewController } from 'ionic-angular';
import { Storage} from '@ionic/storage';

//components
import { MyService } from '../../providers/my-service';
import { AdminPage } from '../admin/admin';

/*
  Generated class for the ModalPage page.

  See http://ionicframework.com/docs/v2/components/#navigation for more info on
  Ionic pages and navigation.
*/
@Component({
  selector: 'page-modal-page',
  templateUrl: 'modal-page.html',
  providers:[MyService]
})
export class ModalPage {

  data:any;
  public local: Storage;
  private mydata:any;

  constructor(public navCtrl: NavController,private viewCtrl: ViewController,private service:MyService) {
    this.data={};
    this.data.username="";
    this.data.password="";
    this.local=new Storage();

  }

  login(){
    let username = this.data.username;
    let password = this.data.password;
    let data  = JSON.stringify({username, password});
    this.service.postLogin(data)
        .subscribe(data => {
          this.mydata = data;
          this.local.set('username', this.mydata[0].name);
          this.local.set('token', this.mydata[0].token);
          this.viewCtrl.dismiss();
        }, error =>{
          console.log(error);
        })
  }
  dismiss(){
    this.viewCtrl.dismiss();
  }

}

这是我的服务页面

    import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import 'rxjs/add/operator/map';
import { Storage} from '@ionic/storage';
import {NavController} from "ionic-angular";

import { AdminPage } from '../pages/admin/admin';
/*
  Generated class for the MyService provider.

  See https://angular.io/docs/ts/latest/guide/dependency-injection.html
  for more info on providers and Angular 2 DI.
*/
@Injectable()
export class MyService {

  public local:Storage;
   private mydata:any;
    public getsession: any;
  constructor(public http: Http,private local: Storage,private navCtrl:NavController) {
    this.local=new Storage();

  }
  postLogin(data){
      let link = "http://adirzoari.16mb.com/newapi.php";
      return this.http.post(link,data)
          .map(res => res.json())
  }
  checkToken(){
      return this.getsession =this.local.get('token');

  }
}

Answer 1

似乎您访问了“element模板中某处modal-page.html”字段。例如，

{{ something.element }}

如果是这样，请尝试使用 {{ some?.element }}。

在访问字段之前检查某物是否存在(不为空或未定义)。