我有src/main/resources/static使用的服务HelperService。
NavComponentComponentnav-component.component.ts
@Injectable()
export class HelperService {
...
}
我正在@Component({
selector: 'app-nav-component',
templateUrl: './nav-component.component.html',
styleUrls: ['./nav-component.component.css'],
providers:[UserManagementService,
HelperService]
})
export class NavComponentComponent implements OnInit {
constructor(private userManagementService: UserManagementService, private fb:FormBuilder, private helper:HelperService) {
}
..
}
中使用NavComponent
AppComponent但是我遇到了错误
<app-nav-component></app-nav-component>
但是当我向服务提供模块级别时，我的程序就可以了！为什么仅在ERROR Error: StaticInjectorError(AppModule)[NavComponentComponent -> HelperService]:
StaticInjectorError(Platform: core)[NavComponentComponent -> HelperService]:
NullInjectorError: No provider for HelperService!
at NullInjector.push../node_modules/@angular/core/fesm5/core.js.NullInjector.get (core.js:1062)
at resolveToken (core.js:1300)
at tryResolveToken (core.js:1244)
at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:1141)
at resolveToken (core.js:1300)
at tryResolveToken (core.js:1244)
at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:1141)
中使用providers:HelperService无效？
答案 0 :(得分：0)
我不确定，但是可能的原因是HelperService也被AuthService使用，而UserManagementService是通过Angular添加的。我认为UserManagementService试图注入HelperService并发现无法添加HelperService。为了解决此问题，我在模块级别注入了providers，以便它对所有组件都可用。
我想知道在组件级别颠倒providers:[UserManagementService, HelperService]中的服务顺序是否可行，但是没有实现，即providers:[HelperService,UserManagementService]和RandomForestClassifier都不起作用