共享服务是非相关组件之间常见的通信方式.您的组件需要使用服务的单个实例，因此请确保它在根级别提供.

Shared service is a common way of communication between non-related components. Your components need to use a single instance of the service, so make sure it's provided at the root level.

使用 BehaviorSubject 作为数据委托的示例:

共享服务:

@Injectable()
export class SharedService {

    isVisibleSource: BehaviorSubject<boolean> = new BehaviorSubject(false);

    constructor() { }
}

组件 1:

export class Component1 {

    isVisible = false;

    constructor(private sharedService: SharedService) { }

    onClick(): void {
        this.isVisible = !this.isVisible;
        this.sharedService.isVisibleSource.next(this.isVisible);
    }
}

组件 2:

export class Component2 {

    constructor(private sharedService: SharedService) { }

    ngOnInit(): void {
        this.sharedService.isVisibleSource.subscribe((isVisible) => {
            console.log('isVisible: ', isVisible); // => true/false
        });
    }
}

值得一提的是，BehaviorSubject 在订阅时返回它持有的最后一个值，因此上面示例中的组件将在实例化后立即更新为最新值.

It is worth mentioning that BehaviorSubject upon a subscription returns the last value it holds, therefore the component from the example above will be updated with the most recent value immediately after the instantiation.

BehaviorSubject 还允许在不订阅的情况下获取其最新值:

BehaviorSubject also allows to get its most recent value without even subscribing to it:

this.sharedService.isVisibleSource.getValue(); // => true/false