在Angular 2.0中注入服务提供者

在AngularJS 2.0 Heroes教程解释中,它指出如果子组件在其@Component Providers列表中包含服务,则Angular将创建特定于该子组件的该服务的单独实例.我不明白的是,如果有时您想独立使用子组件,而有时在父组件中使用子组件,您会怎么做.这似乎是一个严重的限制.我刚刚玩Angular 2.0,所以很可能我误解了一些东西.

以下是来自Heroes Tutorial服务部分的Angular.io网站的解释.

Appendix: Shadowing the parent’s service

We stated earlier that if we injected the parent AppComponent
HeroService into the HeroDetailComponent,we must not add a providers
array to the HeroDetailComponent metadata.

Why? Because that tells Angular to create a new instance of the
HeroService at the HeroDetailComponent level. The HeroDetailComponent
doesn’t want its own service instance; it wants its parent’s service
instance. Adding the providers array creates a new service instance
that shadows the parent instance.

Think carefully about where and when to register a provider.
Understand the scope of that registration. Be careful not to create a
new service instance at the wrong level.

Here’s the link到这个来自的页面把它放在上下文中.

class Service {
    someProp = 'Default value';
}

@Component({
  providers : [Service] // Child's instance
})
class Child {
  constructor(
    @SkipSelf() parentSvc: Service,svc: Service
    ) {
        console.log(pSvc.someProp); // Prints 'Parents instance'
        console.log(svc.someProp);  // Prints 'Default value'
    }
}

@Component({
  providers : [Service] // Parent's instance
})
class Parent {
  constructor(svc: Service) {
    svc.someProp = 'Parent instance';
  }
}