从子组件到父组件的角度5 EventEmitter发射未定义

string 从子组件到父组件。

孩子在这里:

//imports... 

    @Component({
    selector: 'child',
    templateUrl: './child.component.html',
    styleUrls: ['./child.component.css'],
    providers: [ChildService]
    })

export class DataTableComponent implements OnInit {
    constructor(private http: HttpClient, private childService : ChildService) {}

    myMap = new Map<string, ISomeInterface>();
    currentSelection: string;

    @Output() sendDataEvent = new EventEmitter<string>();

    sendData() {
        console.log("sending this data:  " + this.myMap.get(this.currentSelection).name);
        this.sendDataEvent.emit(this.myMap.get(this.currentSelection).name);
    }
}

这是家长:

html->

<d-table (sendDataEvent)="receiveBusinessCycle(event)"></d-table>

//imports...

@Component({
  selector: 'parent',
  templateUrl: './parent.component.html',
  styleUrls: ['./parent.component.css'],
  providers: [ParentService]
})
export class MyParentComponent {
  totoName: string;

  constructor(private parentService : ParentService) {  }

  receiveBusinessCycle($event) {
    console.log($event); //shows in console 'undefined'
    console.log($event as string); 
    this.totoName = $event;
  }

}

问题是我得到了一个 事件接收父组件中的数据时,控制台日志如下:

sending this data:  201808
main.bundle.js:2328 undefined
main.bundle.js:2329 undefined

对这个问题有什么看法吗?