angular - 升级到 Angular 5 NullInjectorError : No provider for

Question

我正在尝试升级到 Angular 4，但是在运行代码时出现错误:
ERROR Error: Uncaught (in promise): Error: StaticInjectorError(AppModule)[AuthenticatedGuard -> AuthService]:
StaticInjectorError(Platform: core)[AuthenticatedGuard -> AuthService]:
NullInjectorError: No provider for AuthService!
该错误显示“没有 AuthService 提供者”，但在我正在导航的组件中，我注入(inject)并成功使用了我的 AuthService。以下是相关的源文件:

app.module.ts

import { AuthService } from '../../services/auth.service';
import { AuthenticatedGuard } from '../../utility/authenticated.gaurd'
@NgModule({
    imports:[ ... ],
    declarations: [ ... ], 
    providers: [ AuthService, AuthenticatedGuard ]})
export class AppModule { }

认证的gaurd.ts

import { Injectable } from '@angular/core';
import { Router, CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot } from '@angular/router';
import { AuthService } from '../services/auth.service.js';

@Injectable()
export class AuthenticatedGuard implements CanActivate {

    constructor(private authService: AuthService, private router: Router) { }

    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): boolean {

        return true;
    }
}

应用程序路由.module.ts

import { AdminComponent }       from '../../components/admin/admin.component';
import { NgModule }             from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

const routes: Routes = [
  { path: 'admin',  component: DashboardComponent, canActivate: [AuthenticatedGuard]},
];

@NgModule({
  imports: [ RouterModule.forRoot(routes) ],
  exports: [ RouterModule ]
})

export class AppRoutingModule {}

这个错误可能神秘地来自哪里？我假设有些东西从 Angular 4 - 5 发生了变化，但我不确定是什么？

Answer 1

第一步:

import { AuthService } from '../services/auth.service';

第二步:

providers: [
    AuthService
],