未定义ViewChild

Question

@ViewChild(AlertComponent) alert: AlertComponent;

  ngAfterViewInit(){
    debugger;
    var msg: Message ={ message: 'Saved successfully!', status: true };
    console.log(this.alert.show(msg))
  }

  success(){
    debugger;
    //Saved successfully show the message
    var msg: Message ={ message: 'Saved successfully!', status: true };
    this.alert.show(msg);
  }

这是我的代码。我无法致电警报服务。它显示了未定义的viewchild

警报组件：

export class AlertComponent {
    message: Message = null;
    constructor() {}
    show(msg: Message) {
        debugger;
        this.message = msg;
        setTimeout(() => {
            this.message = null;
        }, 2000)
    }
}

Answer 1

您应该在父组件的模板中使用Alert Component。无论如何，您应该尝试在输入/输出或服务等组件之间进行另一种类型的通信。 更多信息：https://angular.io/guide/component-interaction