Angular 错误:NullInjectorError:没有FlashMessagesService的提供程序
当用户单击注销按钮时,我使用Angular 2 flash messages显示消息。我在navbar.component.ts和其他一些实验中添加了提供程序,但遇到了相同的错误 以下是我执行的步骤:Angular 错误:NullInjectorError:没有FlashMessagesService的提供程序,angular,mean-stack,angular2-flashmessages,Angular,Mean Stack,Angular2 Flashmessages,当用户单击注销按钮时,我使用Angular 2 flash messages显示消息。我在navbar.component.ts和其他一些实验中添加了提供程序,但遇到了相同的错误 以下是我执行的步骤: npm install angular2-flash-messages --save 步骤1: npm install angular2-flash-messages --save 第二步: 应用程序模块.ts import { FlashMessagesModule } from 'a
npm install angular2-flash-messages --save
步骤1:
npm install angular2-flash-messages --save
第二步:
应用程序模块.ts
import { FlashMessagesModule } from 'angular2-flash-messages';
@NgModule({
imports: [
// other imports
// ...
FlashMessagesModule,
// ...
]
})
import { Component} from '@angular/core';
import { AuthService } from '../services/auth.service';
import { Router } from '@angular/router';
import { FlashMessagesService } from 'angular2-flash-messages';
@Component({
selector: 'app-navbar',
templateUrl: './navbar.component.html',
styleUrls: ['./navbar.component.css']
})
export class NavbarComponent {
constructor(private _auth: AuthService, private flashMessagesService: FlashMessagesService, private _router: Router) { }
onLogoutClick() {
this._auth.logout();
this.flashMessagesService.show('You are logged out', { cssClass: 'alert-info'});
this._router.navigate(['/']);
}
}
步骤3:
app.component.html
<app-navbar></app-navbar>
<div class="container">
<flash-messages></flash-messages>
<router-outlet></router-outlet>
</div>
<li><a href="#" (click)="onLogoutClick()" >Logout</a></li>
步骤5:
navbar.component.html
<app-navbar></app-navbar>
<div class="container">
<flash-messages></flash-messages>
<router-outlet></router-outlet>
</div>
<li><a href="#" (click)="onLogoutClick()" >Logout</a></li>
Use forRoot()方法返回NgModule及其提供程序依赖项
import { FlashMessagesModule } from 'angular2-flash-messages';
@NgModule({
imports: [
// other imports
// ...
FlashMessagesModule.forRoot(),
// ...
]
})
检查此项:您能解释为什么需要forRoot()吗?forRoot()方法返回一个NgModule及其提供程序依赖项