组件中的角度服务调用功能 [英] Angular service call function in component

问题描述

因此，我知道您可以使两个不相关的组件通过服务彼此通信，方法是使一个组件在服务中发出事件，而另一个组件在服务中订阅该事件.

So I know you can have two unrelated components communicate with each other via a service by having one component emit an event in the service and the other subscribe to it in the service.

我的问题:

服务可以直接在组件中调用函数吗?

Can a service call a function in a component directly?

推荐答案

默认情况下不.服务是类的实例，仅此而已.

Not by default. A service is an instance of a class, nothing more.

@Injectable()
class MyService {
}

@Component({
  selector: 'my-component',
  ...
)}
class MyComponent {
  constructor(private myService:MyService) {}
}

@NgModule({
  providers: [MyService],
  ...
})
export class AppModule {}

这样，服务(MyService)实例将传递给MyComponent，仅此而已.服务实例不了解MyComponent.

This way a service (MyService) instance gets passed to MyComponent but that is all. The service instance has no knowledge about MyComponent.

您可能想要的是在服务中添加Observable并在组件中进行订阅.

What you probably want is to add an Observable to your service and subscribe to it in your component.

@Component({
  selector: 'my-component',
  ...
)}
class MyComponent {
  constructor(myService:MyService) {
    myService.someObservable.subscribe(value => doSomething(value));
  }

  doSomething(value) {
    console.debug(value);
  }
}

这样，当Observable someObservable发出另一个值时，服务将调用"组件上的方法.

this way the service "calls" a method on the component when the Observable someObservable emits another value.

有关更多详细信息，请参见检测嵌套属性的更改用于组件输入

For more details see detect change of nested property for component input

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