组件之间的通信服务不起作用

我正在使用 BehaviorSubject 类来更新全局中的通知数 . 我有2个组件：组件通知显示通知列表，您可以将这些通知设置为已读 . Headers 组件显示未读取的通知数，以便让用户知道他错过了网站上的内容 . 由于有2个不同的组件，我正在使用服务通过它们进行通信 .

这里有一些片段：

notification.service.ts

export class NotificationService {
     public notification: BehaviorSubject<Object> = new BehaviorSubject<Object>({});
     public nbNotificationsChange: BehaviorSubject<number>;

constructor(){
     this.nbNotificationsChange = new BehaviorSubject<number>(0);
}

updateNbNotification(value) {
    this.nbNotificationsChange.next(value);
    this.nbNotificationsChange.subscribe(x => console.log(x));
}

getNbNotification(){
    return this.nbNotificationsChange.getValue();
} }

header.component.ts

export class HeaderComponent implements OnInit, DoCheck {
    public notifications: Notification[] = [];
    public nbNotifications: number = 0;


    constructor (public notificationService: NotificationService){
    this.notificationService.nbNotificationsChange.subscribe(value => {
            this.nbNotifications = value;
        });
    }
ngOnInit() {
    this.getNotificationsNotRead();
    this.notificationService.nbNotificationsChange.subscribe(value => {
        this.nbNotifications = value;
    });
}

ngDoCheck(){
    this.nbNotifications = this.notificationService.getNbNotification()
    //console.log("test");
}
getNotificationsNotRead(){
    aNotRelevantFunctionToRetreiveNotification.subscribe(
            this.notifications = //Receive an array of Notifications here with some code
            this.notifications = this.notifications.filter((notif : Notification) => notif.seen == false); // Check if a notification is read or not
            this.notificationService.updateNbNotification(this.notifications.length);
            console.log(this.notifications.length);
    );
}

get nbNotif(): number {
    return this.notificationService.getNbNotification();
} }

notification.component.ts

export class NotificationsComponent implements OnInit {

public notifications: Notification[];

constructor(public notificationService: NotificationService) {}

ngOnInit() {
    this.getAllNotifications();
}

public getAllNotifications() {
    //Receive an array of notifications to display them, passsing this code. We're in the subscribe
    var nbNotifNotRead = this.notifications.filter((notif : Notification) => notif.seen == false).length;
    this.notificationService.updateNbNotification(nbNotifNotRead); //This value is properly set
}
}

问题是，即使在notification.component.ts一侧设置了值，在header.component.ts中检索的值也不是好的，并且是最初的一个，当然不是我想要的 .

有没有人有想法？现在已经在这个问题上挣扎太久了

更新

这是html部分，非常简单：

<span class="SomeCSSClasses" *ngIf="nbNotifications > 0">{{nbNotifications}}</span>

更新2

该模块涉及：

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { HttpModule } from '@angular/http';
/* A lot of imports */

@NgModule({
  imports: [
    CommonModule,
    HttpModule,

  ],
  providers: [
    ApiService,
    CurrencyService,
    /* A lot of services */
    NbNotificationService
    ]
})

export class ServicesModule { }

这是在App.module中导入的原始模块 . 我通过这样创建自己的模块：

import { ModuleWithProviders, NgModule, Optional, SkipSelf } from '@angular/core';

import { NbNotificationService } from './nb-notification.service';
@NgModule({
  providers:    [ NbNotificationService ]
})

export class NbNotificationServiceModule {
    constructor (@Optional() @SkipSelf() parentModule: NbNotificationServiceModule) {
        if (parentModule) {
          throw new Error(
            'NbNotificationServiceModule is already loaded. Import it in the AppModule only');
        }
      }

    static forRoot(): ModuleWithProviders {
        return {
          ngModule: NbNotificationServiceModule,
          providers: [
            {provide: NbNotificationService, useValue: 0 }
          ]
        };
      }
}

试图将此添加到AppModule但它说错误如下： Cannot instantiate cyclic dependency! NbNotificationService ("[ERROR ->]"): in NgModule PagesModule in ./PagesModule@-1:-1