Angular2 module has no exported member

问题

For a website with authentication in Angular2, I want to use a component of the authentication submodule in the main app component. However, I keep getting the following error:

app/app.component.ts(3,10): error TS2305: Module '"<dir>/app/auth/auth.module"' has no exported member 'SigninComponent'.

even after exporting SigninComponent.

The project folder structure is as shown below:

app/auth/auth.module.ts:

import { NgModule }       from '@angular/core';
import { CommonModule }   from '@angular/common';
import { FormsModule }    from '@angular/forms';

import { RegisterComponent }    from './components/register.component';
import { SigninComponent }    from './components/signin.component';
import { HomeComponent }    from './components/home.component';

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

@NgModule({
  imports: [
      CommonModule,
      FormsModule
  ],
  declarations: [
      RegisterComponent,
      SigninComponent,
      HomeComponent
  ],
  providers: [
      AuthService,
      AuthHttp
  ],
  exports: [
      RegisterComponent,
      SigninComponent,
      HomeComponent
  ]
})
export class AuthModule {}

app/auth/components/signin.component.ts:

import { Component } from '@angular/core';
import { Router } from '@angular/router';
import { AuthService } from '../services/auth.service';

@Component({
    selector: 'signin',
    templateUrl: 'app/auth/signin.html'
})
export class SigninComponent {
    ...
}

app/app.component.ts:

import { Component, OnInit } from '@angular/core';
import { Router, RouterOutlet } from '@angular/router';
import { SigninComponent, RegisterComponent } from './auth/auth.module';
import { AuthHttp } from './auth/services/auth-http';
import { AuthService } from './auth/services/auth.service';

@Component({
    selector: 'myapp',
    templateUrl: 'app/app.html'
})

export class AppComponent implements OnInit {
    ...
}

app/app.module.ts:

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule }   from '@angular/forms';
import { HttpModule }    from '@angular/http';
import { RouterModule } from '@angular/router';
import { AppRoutingModule } from './app-routing.module';
import { AuthModule } from './auth/auth.module';

import { AppComponent } from './app.component';

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

@NgModule({
  declarations: [
      AppComponent,
      AuthService,
      AuthHttp
  ],
  bootstrap: [ AppComponent ],
  imports : [
      BrowserModule,
      FormsModule,
      HttpModule,
      AuthModule,
      AppRoutingModule
  ],
  providers: [
      AuthService,
      AuthHttp
  ]
})
export class AppModule {
}

回答1:

You do not need the line:

import { SigninComponent, RegisterComponent } from './auth/auth.module';

in your app.component.ts as you already included the AuthModule in your app.module.ts. AutModule import is sufficient to use your component in the app.

The error that you get is a TypeScript error, not a Angular one, and it is correct in stating that there is no exported member, as it searches for a valid EC6 syntax for export, not angular module export. This line would thus work in your app.component.ts:

import { SigninComponent } from './auth/components/signin.component';

回答2:

Working with atom (1.21.1 ia32)... i got the same error, even though i added a reference to my pipe in the app.module.ts and in the declarations within app.module.ts

solution was to restart my node instance... stopping the website and then doing ng serve again... going to localhost:4200 worked like a charm after this restart

回答3:

Also some of common cases :

maybe you export class with "default" prefix like so

export default class Module {}

just remove it

export class Module {}

this is solve the issue for me

回答4:

For me such issue occur when I had multiple export statements in single .ts file...

回答5:

This error can also occur if your interface name is different than the file it is contained in. Read about ES6 modules for details. If the SignInComponent was an interface, as was in my case, then

SignInComponent

should be in a file named SignInComponent.ts.

回答6:

I got similar issue. The mistake i made was I did not add service in the providers array in app.module.ts. Hope this helps, Thank You.

回答7:

I was facing same issue and I just started app with new port and everything looks good.

ng serve --port 4201

回答8:

In my module i am exporting classes this way:

export { SigninComponent } from './SigninComponent';
export { RegisterComponent } from './RegisterComponent';

This allow me to import multiple classes in file from same module:

import { SigninComponent, RegisterComponent} from "../auth.module";

PS: Of course @Fjut answer is correct, but same time it doesn't support multiple imports from same file. I would suggest to use both answers for your needs. But importing from module makes folder structure refactorings more easier.

回答9:

I had the component name wrong(it is case sensitive) in either app.rounting.ts or app.module.ts.

来源：https://stackoverflow.com/questions/41264962/angular2-module-has-no-exported-member