CODEWITHSUNDEEP
angular
Lambo Jayapalan
Lambo Jayapalan

Reputation: 330

Error: No provider for AuthInterceptor

I'm trying to implement an http interceptor using the new HttpClient in Angular 4.3, but I keep getting the error:

ERROR Error: Uncaught (in promise): Error: No provider for AuthInterceptor!

This is what I have in my app.module.ts:

@NgModule({
bootstrap: [AppComponent],
declarations: [
    AppComponent,
    LoginComponent,
    NotFoundComponent
],
imports: [
    RouterModule.forRoot([
        { path: "", redirectTo: "login", pathMatch: "full" },
        { path: "login", component: LoginComponent },
        { path: "**", component: NotFoundComponent }
    ]),

    NgbModule.forRoot(),
    BrowserAnimationsModule,
    HttpClientModule,
],
providers: [
    AuthenticationService,
    { provide: HTTP_INTERCEPTORS, useExisting: AuthInterceptor, multi: true },
]
};

I've looked into all the articles with the error "No provider for CustomService", and they all refer to making sure that the service is added to the providers list in app.module which I think I've done.

Does anyone have any other ideas?

Thanks.

Upvotes: 1

Views: 4404

Answers (1)

Aluan Haddad
Aluan Haddad

Reputation: 31803

TL;DR: change useExisting to useClass or add AuthInterceptor to your providers array if you want to inject it somewhere else explicitly.

There is likely an error in your provider configuration. Specifically you have registered your AuthInterceptor with the useExisting provider option.

What this does is register an alias for another, existing dependency injection provider under a new token.

The purpose of that would be to make a service which is already provided as AuthInterceptor available for injection via the token HTTP_INTERCEPTORS.

Therefore, unless some other ngModule imported by your application* is already providing something under the token AuthInterceptor, it will fail.

To resolve the problem at hand, change useExisting to useClass, if AuthInterceptor is a class, otherwise change it to useValue or useFactory as needed. Another option would be to add AuthInterceptor to your providers property you would do this if you want to inject it directly somewhere else.

* Note that all providers that are imported via eagerly loaded ngModules are merged into a shared, global dependency injection container.

Upvotes: 4

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