在 Angular 中注入 URL 6 延迟加载模块之间共享的服务

Question

When I created a service shared between two lazy loaded modules with a different injected URL string, the module URL is logged right in the service constructor but not updated in the service function that does HTTP request.

场景：首先我导航到 module1，响应正确返回了 module1 项目，然后我导航到模块，HTTP 请求由 module1 URL 发送所以它返回了错误的项目

共享服务.ts

@Injectable()
export class SharedService {
  constructor(
    private http: HttpClient,
    @Inject('BASE_URL_TOKEN') private url: string
  ) {
console.log(this.url); // prints the right value
}
  getItems(invoiceCode: string): Observable<any> {
   console.log(this.url); // prints the old value
    return this.http.get(
      this.url + RestUrls.ITEMS_URL,
      httpOptions
    );
  }

}

shared.module.ts

export const BASE_URL_TOKEN = 'BASE_URL_TOKEN';

@NgModule({
  imports: [
    CommonModule,
  ],
  declarations: [
    Components.ViewInvoiceItemsComponent
  ],
  exports: [
    Components.ViewItemsComponent,
  ]
})
export class SharedModule {}

模块1.module.ts

    @NgModule({
      imports: [
        SharedModule,
      ],
      declarations: [
        HomeScreenComponent,
      ],
      providers: [
SharedService,
        [
          { provide: BASE_URL_TOKEN, useValue: 'module1/' }
        ]
      ]
    })
    export class Module1 {}

模块2.module.ts

    @NgModule({
      imports: [
        SharedModule,
      ],
      declarations: [
        HomeScreenComponent,
      ],
      providers: [
SharedService,
        [
          { provide: BASE_URL_TOKEN, useValue: 'module2/' }
        ]
      ]
    })
    export class Module2 {}

Answer 1

BASE_URL_TOKEN 值在 Shared 模块创建 SharedService 实例时设置。 SharedService 无法知道 BASE_URL_TOKEN 值的变化。 在您的情况下，要使其正常工作，您必须在每个模块上创建 SharedService 的新实例或明确告知 SharedService 您要使用的值。 另外，请阅读有关InjectionToken