组件订阅不会看到具有Subject Observable调用next()的Angular Service

当我通过组件中提供的服务订阅Subject时,我发现即使从BorrowerService调用.next(),也永远不会调用onNext()函数参数.

如果我在BorrowerService类中订阅,我发现.next()按预期工作.似乎Subject是调用.next()的Service类和组件之间的不同实例,因此不会获得该订阅.

这是否无法理解Angular Services或Observables？如何在不知道何时调用.next()的情况下更新服务中的值并被动地获取组件中的更改？

借款人-report.component.ts

@Component({
    ...
    providers:   [BorrowerService]
})
export class BorrowerReport {
    private borrower: Borrower;

    constructor(private borrowerService: BorrowerService) {
        this.borrowerService.borrowerChanged.subscribe(borrower => {this.borrower = borrower});
    }
}

borrower.service.ts

@Injectable()
export class BorrowerService {
    public borrowerChanged: Subject<Borrower> = new Subject<Borrower>();

    //event handler
    selectBorrower(borrower: Borrower) {
        this.borrowerChanged.next(borrower);
    }
}