如何在angular2中的两个模块之间共享服务

import { Injectable } from '@angular/core';

@Injectable()
export class SharedService {
  sharedData: string;

  constructor() { }
}

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

import { SharedService } from './shared.service';
import { ComponentA } from './component-a.component';

@NgModule({
  declarations: [
    ComponentA
  ],
  imports: [
    CommonModule
  ],
  providers: [
    SharedService
  ]
})
export class ModuleA { }

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

import { SharedService } from './shared.service';
import { ComponentB } from './component-b.component';

@NgModule({
  declarations: [
    ComponentB
  ],
  imports: [
    CommonModule
  ],
  providers: [
    SharedService
  ]
})
export class ModuleB { }

import { Component } from '@angular/core';
import { SharedService } from './shared.service';

@Component({
  selector: 'app-component-a',
  template: `
    <h1>Component A</h1>
    <p>Shared Data: {{ sharedService.sharedData }}</p>
  `
})
export class ComponentA {
  constructor(private sharedService: SharedService) { }
}

import { Component } from '@angular/core';
import { SharedService } from './shared.service';

@Component({
  selector: 'app-component-b',
  template: `
    <h1>Component B</h1>
    <p>Shared Data: {{ sharedService.sharedData }}</p>
  `
})
export class ComponentB {
  constructor(private sharedService: SharedService) { }
}