angular 7无法读取http回调中的公共变量

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

@Injectable()
export class DataService {
  public commonVariable: any;

  constructor(private http: HttpClient) { }

  getData() {
    return this.http.get('your-api-url').toPromise()
      .then((response) => {
        this.commonVariable = response;
        console.log(this.commonVariable); // 可以访问和使用公共变量
      })
      .catch((error) => {
        console.error(error);
      });
  }
}