Component is part of the declaration of 2 modules

Question

I try to build an ionic 2 app. When I try the app in the browser with ionic serve or launch it on an emulator everything works fine.

But when I try to build it every time the error

ionic-app-script tast: "build"
Error Type AddEvent in "PATH"/add.event.ts is part of the declarations of 2 modules: AppModule in "PATH"/app.modules.ts and AddEvent in "PATH"/add-event.module.ts.
Please consider moving AddEvent in "PATH"/add-event.ts to a higher module that imports AppModule in "PATH"/app.module.ts and AddEventModule.
You can also creat a new NgModule that exports and includes AddEvent then import that NgModule in AppModule and AddEventModule

my AppModule is

import { NgModule, ErrorHandler } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { IonicApp, IonicModule, IonicErrorHandler } from 'ionic-angular';
import { AngularFireModule } from 'angularfire2';
import { MyApp } from './app.component';
import { Eventdata } from '../providers/eventdata';
import { AuthProvider } from '../providers/auth-provider';
import { HttpModule } from '@angular/http';

import { HomePage } from '../pages/home/home';
import { Login } from '../pages/login/login';
import { Register } from '../pages/register/register';
import { AddEvent } from '../pages/add-event/add-event';
import { EventDetails } from '../pages/event-details/event-details';

import { StatusBar } from '@ionic-native/status-bar';
import { SplashScreen } from '@ionic-native/splash-screen';


@NgModule({
  declarations: [
    MyApp,
    HomePage,
    Login,
    Register,
    AddEvent,
    EventDetails

  ],
  imports: [
    BrowserModule,
    IonicModule.forRoot(MyApp),
    HttpModule,
    AngularFireModule.initializeApp(config)
  ],
  bootstrap: [IonicApp],
  entryComponents: [
    MyApp,
    HomePage,
    Login,
    Register,
    AddEvent,
    EventDetails
  ],
  providers: [
    StatusBar,
    SplashScreen,
    {provide: ErrorHandler, useClass: IonicErrorHandler}, Eventdata, AuthProvider
  ]
})
export class AppModule {}

and my add-event.module.ts is

import { NgModule } from '@angular/core';
import { IonicPageModule } from 'ionic-angular';
import { AddEvent } from './add-event';

@NgModule({
  declarations: [
    AddEvent,
  ],
  imports: [
    IonicPageModule.forChild(AddEvent),
  ],
  exports: [
    AddEvent
  ]
})
export class AddEventModule {}

I understand that I have to remove one of the declarations, but I dont know how.

If I remove the declaration from AppModule I get an Error that the Login Page is not found, while running ionic serve

Answer 1

To surpass this error , you should start by removing all the imports of app.module.ts and have something like this :

            import { BrowserModule } from '@angular/platform-browser';
            import { HttpClientModule } from '@angular/common/http';
            import { ErrorHandler, NgModule } from '@angular/core';
            import { IonicApp, IonicErrorHandler, IonicModule } from 'ionic-angular';
            import { SplashScreen } from '@ionic-native/splash-screen';
            import { StatusBar } from '@ionic-native/status-bar';

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


            @NgModule({
              declarations: [
                MyApp
              ],
              imports: [
                BrowserModule,
                HttpClientModule,
                IonicModule.forRoot(MyApp)
              ],
              bootstrap: [IonicApp],
              entryComponents: [
                MyApp
              ],
              providers: [
                StatusBar,
                SplashScreen,
                {provide: ErrorHandler, useClass: IonicErrorHandler}
              ]
            })
            export class AppModule {}

Next edit your pages module , like this :

            import { NgModule } from '@angular/core';
            import { IonicPageModule } from 'ionic-angular';
            import { HomePage } from './home';

            @NgModule({
              declarations: [
                HomePage,
              ],
              imports: [
                IonicPageModule.forChild(HomePage),
              ],
              entryComponents: [HomePage]
            })
            export class HomePageModule {}

Then add annotation of IonicPage before component annotation of all the pages :

import { IonicPage } from 'ionic-angular';

@IonicPage()
@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})

Then edit your rootPage type to be string and remove the imports of pages (if there is any in your app component )

rootPage: string = 'HomePage';

Then the navigation function should be like this :

 /**
* Allow navigation to the HomePage for creating a new entry
*
* @public
* @method viewHome
* @return {None}
*/
 viewHome() : void
 {
  this.navCtrl.push('HomePage');
 }

You can find the source of this solution here : Component is part of the declaration of 2 modules

Answer 2

Solution is very simple. Find *.module.ts files and comment declarations. In your case find addevent.module.ts file and remove/comment one line below:

@NgModule({
  declarations: [
    // AddEvent, <-- Comment or Remove This Line
  ],
  imports: [
    IonicPageModule.forChild(AddEvent),
  ],
})

This solution worked in ionic 3 for pages that generated by ionic-cli and works in both ionic serve and ionic cordova build android --prod --release commands!

Be happy...