Question

我有关于Angular 2的流行错误。当我从另一个组件调用函数时，我遇到了这个错误。

"Cannot read property 'onChange' of undefined at CD019.onChangeParent"

我的代码如下：

  @ViewChild('testComponent') testComponent: CD020;

onChangeParent() {
    this.testComponent.onChange;

}

和子组件是

   @Output() childChanged = new EventEmitter<string>();
    onChange(value: string, test: string) {
        this.childChanged.emit(value);
        this.Test(test);
    }

感谢您的帮助。

Answer 1

根据文档，您应使用组件类型作为ViewChild装饰器的标识符。 https://angular.io/docs/ts/latest/api/core/index/ViewChild-decorator.html

@ViewChild(CD020) testComponent: CD020;

Answer 2

您需要确保@ViewChild(ChildType) testComponent: ChildType使用相同类型的E.g.your子组件：

@Component({
  selector: 'app-my-child',
  templateUrl: './my-child.component.html',
  styleUrls: ['./my-child.component.css']
})
export class CD020 implements OnInit {
    ngOnInit() {
    }
    @Output() childChanged = new EventEmitter<string>();
    onChange(value: string, test: string) {
        this.childChanged.emit(value);
    }
}

你的父母html：

<app-my-child></app-my-child> <!-- uses the template selector name -->

您的父代码：

//note the name inside the viewChild and the type of testComponent
@ViewChild(CD020) testComponent: CD020;

onChangeParent() {
    // must pass two arguments.
    this.testComponent.onChange("someValue","someTest");

}

调用函数时无法读取未定义错误的属性'onchange'

2 个答案: