Error: Angular2 is throwing a TypeError because the property newUser is not defined in the context

Whenever I attempt to include an input field on the template, I encounter this error message:

TypeError: self.context.newUser is undefined

This is the component in question.

import { Component } from '@angular/core';
import { OnInit } from '@angular/core';
import { Router } from '@angular/router';
import { User } from './user';
import { UserService } from './user.service';


@Component({
  selector: 'vista3',
  templateUrl: 'app/vista3.component.html',
  styleUrls:['app/vista3.component.css']
})

export class Vista3Component implements OnInit{
  users: User[] = [];
  newUser: User;

  constructor(
    private router: Router,
    private userService: UserService) {
  }

  ngOnInit(){
    this.userService.getUsers().then( users => this.users = users);
  }
}

The template code snippet is as follows:

<div  class="separar">
  <table class="table table-striped">
      <tr>
        <th>Nombre</th>
        <th>Apellido</th>
      </tr>
        <tr *ngFor="let user of users">
          <td>{{user.name}}</td><td>{{user.lastName}}</td>
        </tr>
  </table>
</div>
<div  class="separar">
  <div class="row">
    <div class="col-xs-12 col-md-3">
      Nombre: <input [(ngModel)]="newUser.name"/>
    </div>
  </div>
</div>

Also, here is the User class defined for reference.

export class User{
  name: string;
  lastName: string;
}

I am relatively new to Angular 2 and Typescript, so identifying the issue has been a challenge. Any help or insight would be greatly appreciated.

Answer №1

  1. You seem to forget assigning any value to the newUser class member.

  2. An error is present in the trigger on the line [(ngModel)]="newUser.name".

Attempting to retrieve name from undefined. Using the ?. operator would be a good solution.

<input [(ngModel)]="newUser?.name"/>

Additionally, make sure to create an empty user in the constructor:

  constructor(
    private router: Router,
    private userService: UserService) {

    this.newUser = new User;
  }

Answer №2

Make sure to initialize the newUser variable before accessing newUser.name

To initialize, you can use the following code snippet:

newUser: User = new User();

Don't forget to update the User class by adding a Constructor as shown below:

export class User{
    constructor(
        public name?: string,
        public lastName?: string
    ) { }
}

I hope this solution helps clarify things!

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