Question

我已经创建了一些应该在整个应用程序中共享的服务，但由于某种原因，子组件会抛出错误 Error: DI Exception at NoProviderError.BaseException [as constructor] 我已经提供了启动文件中的所有服务

bootstrap(AppComponent, [
    JwtHelper,
    HTTP_PROVIDERS, authervice, ROUTER_PROVIDERS, 
    categoryService,
    Configuration
]);

任何人都可以提出建议吗？如果您需要更多解释或代码，请告诉我。

类别组件

import ...
import {categoryService}       from './categoryService';
@Component({
    selector: 'category-list',
    template: `...`,
    directives: [],
    styles: ['.error {color:red;}'],
    providers: []

})
export class categoryComponent implements OnInit {
    constructor(private _categoryService: categoryService) { }
    ...
}

如果我在上面的提供程序中添加categoryservice，则无法正常抛出错误

完成错误

EXCEPTION：错误：未捕获（在承诺中）：EXCEPTION：错误：0：0 原始例外：没有categoryService的提供者！原版的 STACKTRACE：错误：DI异常在NoProviderError.BaseException [作为构造函数]（http://localhost:58056/libs/@angular/core/src/facade/exceptions.js:17:23）在NoProviderError.AbstractProviderError [作为构造函数]（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:39:16）在新的NoProviderError（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:75:16）在ReflectiveInjector _._ throwOrNull（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:776:19）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:804:25）在ReflectiveInjector _._ getByKey（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:767:25）在ReflectiveInjector_.get（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:576:21）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:801:24）错误上下文：[object Object] zone.js：461未处理的Promise rejection：EXCEPTION：错误：0：0原始异常：没有提供者对于categoryService！ ORIGINAL STACKTRACE：错误：DI异常在NoProviderError.BaseException [作为构造函数]（http://localhost:58056/libs/@angular/core/src/facade/exceptions.js:17:23）在NoProviderError.AbstractProviderError [作为构造函数]（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:39:16）在新的NoProviderError（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:75:16）在ReflectiveInjector _._ throwOrNull（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:776:19）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:804:25）在ReflectiveInjector _._ getByKey（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:767:25）在ReflectiveInjector_.get（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:576:21）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:801:24）错误上下文：[object Object];区域：角;任务：Promise.then; 值：ViewWrappedException {_wrapperMessage：“错误：0：0”， _originalException：NoProviderError，_originalStack：“错误：DI异常处于 NoProviderError.BaseExc ... ngular /核心/ src目录/ DI / reflective_injector.js：801：24）”， _context：DebugContext，_wrapperStack：“错误：错误：0：0↵在ViewWrappedException.W ... localhost：58056 / libs / zone.js / dist / zone.js：322：35）”} consoleError @ zone.js：461_loop_1 @ zone.js：490drainMicroTaskQueue @ zone.js：494ZoneTask.invoke @ zone.js：426 zone.js：463错误：未捕获（承诺）：EXCEPTION：错误：0：0原始例外：没有提供者对于categoryService！ ORIGINAL STACKTRACE：错误：DI异常在NoProviderError.BaseException [作为构造函数]（http://localhost:58056/libs/@angular/core/src/facade/exceptions.js:17:23）在NoProviderError.AbstractProviderError [作为构造函数]（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:39:16）在新的NoProviderError（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:75:16）在ReflectiveInjector _._ throwOrNull（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:776:19）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:804:25）在ReflectiveInjector _._ getByKey（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:767:25）在ReflectiveInjector_.get（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:576:21）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:801:24）错误上下文：[object Object] 在NoProviderError.BaseException [作为构造函数]（http://localhost:58056/libs/@angular/core/src/facade/exceptions.js:17:23）在NoProviderError.AbstractProviderError [作为构造函数]（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:39:16）在新的NoProviderError（http://localhost:58056/libs/@angular/core/src/di/reflective_exceptions.js:75:16）在ReflectiveInjector _._ throwOrNull（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:776:19）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:804:25）在ReflectiveInjector _._ getByKey（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:767:25）在ReflectiveInjector_.get（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:576:21）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ElementInjector.get（http://localhost:58056/libs/@angular/core/src/linker/element_injector.js:23:48）在ReflectiveInjector _._ getByKeyDefault（http://localhost:58056/libs/@angular/core/src/di/reflective_injector.js:801:24）错误上下文：[object Object] at resolvePromise（http://localhost:58056/libs/zone.js/dist/zone.js:538:32）在http://localhost:58056/libs/zone.js/dist/zone.js:574:18 在ZoneDelegate.invokeTask（http://localhost:58056/libs/zone.js/dist/zone.js:356:38） at Object.NgZoneImpl.inner.inner.fork.onInvokeTask（http://localhost:58056/libs/@angular/core/src/zone/ng_zone_impl.js:36:41）在ZoneDelegate.invokeTask（http://localhost:58056/libs/zone.js/dist/zone.js:355:43）在Zone.runTask（http://localhost:58056/libs/zone.js/dist/zone.js:256:48）在drainMicroTaskQueue（http://localhost:58056/libs/zone.js/dist/zone.js:474:36）在XMLHttpRequest.ZoneTask.invoke（http://localhost:58056/libs/zone.js/dist/zone.js:426:22)consoleError @ zone.js：463_loop_1 @ zone.js：490drainMicroTaskQueue @ zone.js：494ZoneTask.invoke @ zone.js：426

Answer 1

SystemJs 区分大小写（按设计）。如果在项目文件中使用不同的路径名，请执行以下操作：

<强> main.ts

import { categoryService } from './categoryService';

<强> 类别-component.ts

import { categoryService } from './categoryservice';

然后系统js将进行双重导入

这样，angular2将在提供者Map键中找到服务对象的其他实例。

尽管Map对象中存在键。

地图的

has方法将返回false。这就是你收到错误的原因。

请参阅此页面https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Map#Key_equality

中有关Map对象中关键字相等性的更多信息

Answer 2

我认为您在引导应用程序时以正确的方式指定提供程序。

您可能无法在引导模块中正确导入您的服务。您可以在此处检查categoryService是否未定义：

import { categoryService } from './something';

console.log(categoryService); // <-----

bootstrap(AppComponent, [
  JwtHelper,
  HTTP_PROVIDERS, authervice, ROUTER_PROVIDERS, 
  categoryService,
  Configuration
]);

在angular2

2 个答案: