将Typescript类作为Angular中的成员变量？

export class UserService {
  private users: string[] = [];

  addUser(user: string) {
    this.users.push(user);
  }

  getUsers() {
    return this.users;
  }
}

import { Component } from '@angular/core';
import { UserService } from './user.service';

@Component({
  selector: 'app-root',
  template: `
    <h1>Users</h1>
    <ul>
      <li *ngFor="let user of userService.getUsers()">{{ user }}</li>
    </ul>
  `,
})
export class AppComponent {
  constructor(public userService: UserService) {}

  addUser(user: string) {
    this.userService.addUser(user);
  }
}

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { UserService } from './user.service';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule],
  providers: [UserService],
  bootstrap: [AppComponent],
})
export class AppModule {}