Angular 5 中服务的生命周期是什么

服务可以有2个作用域.

如果在您的模块上声明了服务，那么您将为所有人共享相同的实例，这意味着服务将在创建需要它的第一个组件/指令/服务/管道时被构造.然后，当模块本身被销毁时，它将被销毁(大多数情况下，当页面被卸载时)

如果服务是在组件/指令/管道上声明的，那么每次创建组件/指令/管道时将创建一个实例，并在销毁相关组件/指令/管道时销毁一个实例.

You can see it in action

代码测试:制作2个服务，用于显示创建/销毁服务的时间.

@NgModule({
  providers: [GlobalService] // This means lifeCycle is related to the Module, and only one instance is created for the whole module. It will be created only when the first element who needs it will be created.
})
export class AppModule { }

第二个服务是本地组件服务，将为每创建hello-component个实例创建一个服务，并将在销毁hello-component个实例之前销毁.

@Injectable()
export class LocalService implements OnDestroy{
  constructor() {
    console.log('localService is constructed');
  }

  ngOnDestroy() {
    console.log('localService is destroyed');
  }
}

@Component({
  selector: 'hello',
  template: `<h1>Hello {{name}}!</h1>`,
  styles: [`h1 { font-family: Lato; }`],
  providers: [LocalService]
})
export class HelloComponent implements OnInit, OnDestroy {
  @Input() name: string;

  constructor(private localService: LocalService, private globalService: GlobalService) {}

  ngOnInit(){
    console.log('hello component initialized');
  }

  ngOnDestroy() {
    console.log('hello component destroyed');
  }
}

如您所见，Service英寸的Angular 可以有OnDestroy个生命周期钩子.