在angular 6中如何从一个服务调用另一个服务

import { Injectable } from '@angular/core';
import { ServiceB } from './service-b';

@Injectable()
export class ServiceA {
  constructor(private serviceB: ServiceB) { }

  // 在服务A中可以使用serviceB的方法和属性
}

import { Injectable } from '@angular/core';
import { ServiceB } from './service-b';

@Injectable()
export class ServiceA {
  constructor(private serviceB: ServiceB) { }

  callServiceBMethod() {
    this.serviceB.someMethod();
  }
}

import { Component } from '@angular/core';
import { ServiceA } from './service-a';

@Component({
  selector: 'app-my-component',
  template: `
    <button (click)="callServiceBMethod()">调用服务B的方法</button>
  `
})
export class MyComponent {
  constructor(private serviceA: ServiceA) { }

  callServiceBMethod() {
    this.serviceA.callServiceBMethod();
  }
}