angular – TypeError：instance [output.propName] .subscribe不是函数

家长：

parent.ts

onChangeUpload(event){
  console.log('event');
  console.log(event);
}

<app-upload (uploadEmit)="onChangeUpload($event)"></app-upload>

儿童：

@Output() uploadEmit: EventEmitter = new EventEmitter();

thiS.UploadEmit.emit('upload successful');

我收到了这个错误：

core.js:1448 ERROR Error: Uncaught (in promisE): TypeError: instance[output.propName].subscribe is not a function

@angular/cli: 1.7.3
@angular-devkit/build-optimizer: 0.3.2
@angular-devkit/core: 0.3.2
@angular-devkit/scheR_861_11845@atics: 0.3.2
@ngtools/json-scheR_861_11845@a: 1.2.0
@ngtools/webpack: 1.10.2
@scheR_861_11845@atics/angular: 0.3.2
@scheR_861_11845@atics/package-@R_618_9531@e: 0.3.2
typescript: 2.6.2
webpack: 3.11.0