javascript - RXJS 的 Subject inside Function

Question

请，我需要帮助我的代码不起作用：

this.howToUseObservables().subscribe(ress => alert('in app ' + ress));

为什么testSubject.next('test');根本不开火？谢谢

howToUseObservables(): Subject<any> {
const testSubject: Subject<any> = new Subject();
testSubject.next('test');
return testSubject;
}

this.howToUseObservables().subscribe(ress => alert('in app ' +ress));