1. 通过订阅Observable对象来等待API调用返回数据。在组件中定义一个Observable对象并订阅它，当API调用返回数据时，数据将通过订阅的回调函数传递给组件。

import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Component({
  selector: 'app-my-component',
  template: `{{ data }}`
})
export class MyComponent {
  data$: Observable;

  constructor(private http: HttpClient) {
    this.data$ = http.get('https://api.example.com/data');
    this.data$.subscribe(data => console.log(data));
  }
}

2. 使用async/await语法等待API调用返回数据。在组件中定义一个异步方法，使用async/await关键字等待API调用返回数据，然后将数据分配给组件的成员变量。

import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Component({
  selector: 'app-my-component',
  template: `{{ data }}`
})
export class MyComponent {
  data: any;

  constructor(private http: HttpClient) {
    this.getData();
  }

  async getData() {
    try {
      this.data = await this.http.get('https://api.example.com/data').toPromise();
      console.log(this.data);
    } catch (error) {
      console.error(error);
    }
  }
}