如何在Angular中订阅服务

// 1. 创建一个服务
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private data: Observable<any>;

  constructor() {
    // 模拟异步获取数据
    this.data = new Observable(observer => {
      setTimeout(() => {
        observer.next('Hello, World!');
        observer.complete();
      }, 2000);
    });
  }

  getData(): Observable<any> {
    return this.data;
  }
}

// 2. 在组件中注入服务
import { Component, OnInit } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-my-component',
  template: `
    <div>{{ message }}</div>
  `
})
export class MyComponent implements OnInit {
  message: string;

  constructor(private dataService: DataService) {}

  ngOnInit() {
    // 3. 订阅服务
    this.dataService.getData().subscribe(data => {
      this.message = data;
    });
  }
}