实施 CanDeactivate Guard 时出错

Question

我目前正在尝试为我的 Angular 应用程序实现 CanDeactivate Guard，该应用程序已经具有 HTTP 拦截器来解析身份验证。 但是添加 CanDeactivate 守卫会引发错误，如下所述。

我已经在 AppModule 的 providers 数组中注册了实现 CanDeactivate 接口的类。 我已经在路由的 canDeactivate 属性中注册了实现 CanDeactivate 接口的类。

实现 CanDeactivate 接口的类：

export interface CanComponentDeactivate {
  canComponentDeactivate(): boolean;
}

@Injectable({providedIn: 'root'})
export class AppRegisterDeactivateGuard implements CanDeactivate<AppRegisterComponent> {
  canDeactivate(
    component: AppRegisterComponent,
    currentRoute: ActivatedRouteSnapshot,
    currentState: RouterStateSnapshot
  ): Observable<boolean>|Promise<boolean>|boolean {
    return component.isDeactivated;
  }
}

应用了 Deactivate 防护的组件：

@Component({
  selector: 'app-app-register',
  templateUrl: './app-register.component.html',
  styleUrls: ['./app-register.component.css']
})
export class AppRegisterComponent implements OnInit, CanComponentDeactivate {
  isDeactivated = false;
  @ViewChild('registrationForm') registForm: NgForm;
.
.
canComponentDeactivate() {
    if (this.registForm.dirty) {
      this.isDeactivated = confirm('You have modified changes in the form. \nDo you still want to navigate away ? ');
    }
    return this.isDeactivated;
  }
}

该端点的路由定义：

...
{ path: 'register', component: AppRegisterComponent, canDeactivate: ['AppRegisterDeactivateGuard'] },

模块中的Providers数组：

 providers: [{
    provide: HTTP_INTERCEPTORS,
    useClass: AppAuthInterceptService,
    multi: true
  }, AppRegisterDeactivateGuard],
  bootstrap: [AppComponent]

错误

  StaticInjectorError(Platform: core)[AppRegisterDeactivateGuard]: 
    NullInjectorError: No provider for AppRegisterDeactivateGuard!
Error: StaticInjectorError(AppModule)[AppRegisterDeactivateGuard]: 
  StaticInjectorError(Platform: core)[AppRegisterDeactivateGuard]: 
    NullInjectorError: No provider for AppRegisterDeactivateGuard!
    at NullInjector.push../node_modules/@angular/core/fesm5/core.js.NullInjector.get (core.js:8896)
    at resolveToken (core.js:9141)
    at tryResolveToken (core.js:9085)
    at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:8982)
    at resolveToken (core.js:9141)
    at tryResolveToken (core.js:9085)
    at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:8982)
    at resolveNgModuleDep (core.js:21218)
    at NgModuleRef_.push../node_modules/@angular/core/fesm5/core.js.NgModuleRef_.get (core.js:21907)
    at getToken (router.js:2865)
    at resolvePromise (zone.js:831)
    at resolvePromise (zone.js:788)
    at zone.js:892
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:423)
    at Object.onInvokeTask (core.js:17290)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:422)
    at Zone.push../node_modules/zone.js/dist/zone.js.Zone.runTask (zone.js:195)
    at drainMicroTaskQueue (zone.js:601)
    at ZoneTask.push../node_modules/zone.js/dist/zone.js.ZoneTask.invokeTask [as invoke] (zone.js:502)
    at invokeTask (zone.js:1744)

Answer 1

TLDR; 将您的路线更改为：

{ path: 'register', component: AppRegisterComponent, canDeactivate: [AppRegisterDeactivateGuard] }

将您的提供者更改为：

[{
    provide: HTTP_INTERCEPTORS,
    useClass: AppAuthInterceptService,
    multi: true
  }]

更长的答案：

AppRegisterDeactivateGuard 同时具有{providedIn: 'root'} 并将其声明为模块中的提供者是不必要的。 See the Angular provider docs.

这里的问题是路由和提供者的组合。

现在您的路由正在通过字符串名称查找令牌，但它可以通过类名获得。

使用@Injectable({providedIn: 'root'})，你如何拥有它使用类名作为令牌，它将作为 AppRegisterDeactivateGuard 提供。

在您的提供商中拥有AppRegisterDeactivateGuard，您如何拥有它也将使其可用作 AppRegisterDeactivateGuard。

我不推荐这样做，但是如果您想或需要通过字符串名称引用它，您可以将它放在提供程序中，如下所示：

{ provide: 'AppRegisterDeactivateGuard', useClass: AppRegisterDeactivateGuard }

Answer 2

你需要在泛型中传递接口：

export class AppRegisterDeactivateGuard implements CanDeactivate<CanComponentDeactivate > {

然后实现canDeactivate方法