angular2 构建问题 useFactory 与功能

Question

作为 Angular 的初学者，我在尝试通过 angular-cli 构建我的应用程序时遇到了一个问题。

关注此tutorial之后:

我的 appModule 看起来像:

...
providers: [
{ provide: HttpService, useFactory: (backend: XHRBackend, options:     RequestOptions) => {
return new HttpService(backend, options); },
  deps: [XHRBackend, RequestOptions]}
]
...

构建它时我得到:

Error: Error encountered resolving symbol values statically. Function calls are
not supported. Consider replacing the function or lambda with a reference to an
exported function (position 63:39 in the original .ts file), resolving symbol Ap
pModule in ../angular/app/src/app/app.module.ts
at positionalError (..\angular\app\node_modules\@angular\compiler-c
li\src\static_reflector.js:595:18)

当我使用 ng serve 时，应用程序可以正常运行。

Answer 1

试试这个:

export function httpServiceFactory(backend: XHRBackend, options: RequestOptions) {
  return new HttpService(backend, options);
}  
  
providers: [
  { 
    provide: HttpService, 
    useFactory: httpServiceFactory,
    deps: [XHRBackend, RequestOptions]
  }
]

当您构建它时，它会尝试进行 AoT 编译，但在遇到 lambda 函数时会失败，因此您需要导出它。当使用 ng-serve 时，它​​使用 JiT 编译。

参见:https://github.com/angular/angular/issues/11262#issuecomment-244266848