Angular 2-从组件到类的外部访问变量(无父关系，子关系)

// 定义一个服务
@Injectable()
export class DataService {
  private data: string;

  setData(data: string) {
    this.data = data;
  }

  getData() {
    return this.data;
  }
}

// 在提供商中注册服务
@NgModule({
  providers: [DataService]
})
export class AppModule { }

// 组件A，设置数据
@Component({
  selector: 'component-a',
  template: `
    <button (click)="setData()">Set Data</button>
  `
})
export class ComponentA {
  constructor(private dataService: DataService) {}

  setData() {
    this.dataService.setData('Hello from Component A');
  }
}

// 组件B，获取数据
@Component({
  selector: 'component-b',
  template: `
    <div>{{ getData() }}</div>
  `
})
export class ComponentB {
  constructor(private dataService: DataService) {}

  getData() {
    return this.dataService.getData();
  }
}