Component is part of the declaration of 2 modules

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 create 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 don't know how.

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

Remove the declaration from AppModule, but update the AppModule configuration to import your AddEventModule.

.....
import { AddEventModule } from './add-event.module';  // <-- don't forget to import the AddEventModule class

@NgModule({
  declarations: [
    MyApp,
    HomePage,
    Login,
    Register,
    //AddEvent,  <--- remove this
    EventDetails

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

Also,

Note that it's important that your AddEventModule exports the AddEvent component if you want to use it outside that module. Luckily, you already have that configured, but if it was omitted, you would've gotten an error if you tried to use the AddEvent component in another component of your AppModule

Some people using Lazy loading are going to stumble across this page.

Here is what I did to fix sharing a directive.

1. create a new shared module

shared.module.ts

import { NgModule, Directive,OnInit, EventEmitter, Output, OnDestroy, Input,ElementRef,Renderer } from '@angular/core';
import { CommonModule } from '@angular/common';

import { SortDirective } from './sort-directive';

@NgModule({
  imports: [
  ],
  declarations: [
  SortDirective
  ],
  exports: [
    SortDirective
  ]
})

export class SharedModule { }

Then in app.module and your other module(s)

import {SharedModule} from '../directives/shared.module'
...

@NgModule({
   imports: [
       SharedModule
       ....
       ....
 ]
})
export class WhateverModule { }

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...

If your pages is created by using CLI then it creates a file with filename.module.ts then you have to register your filename.module.ts in imports array in app.module.ts file and don't insert that page in declarations array.

eg.

import { LoginPageModule } from '../login/login.module';


declarations: [
    MyApp,
    LoginPageModule,// remove this and add it below array i.e. imports
],

imports: [
        BrowserModule,
        HttpModule,
        IonicModule.forRoot(MyApp, {
           scrollPadding: false,
           scrollAssist: true,
           autoFocusAssist: false,
           tabsHideOnSubPages:false
        }),
       LoginPageModule,
],

IN Angular 4. This error is considered as ng serve run time cache issue.

case:1 this error will occur, once you import the component in one module and again import in sub modules will occur.

case:2 Import one Component in wrong place and removed and replaced in Correct module, That time it consider as ng serve cache issue. Need to Stop the project and start -do again ng serve, It will work as expected.

This module is added automatically when you run ionic command. However it's not necessery. So an alternative solution is to remove add-event.module.ts from the project.

You may just try this solution ( for Ionic 3 )

In my case, this error happen when i call a page by using the following code

 this.navCtrl.push("Login"); // Bug

I just removed the quotes like the following and also imported that page on the top of the file which i used call the Login page

> this.navCtrl.push(Login); // Correct

I can't explain the difference at this time since i'm a beginner level developer

Since the Ionic 3.6.0 release every page generated using Ionic-CLI is now an Angular module. This means you've to add the module to your imports in the file src/app/app.module.ts

import { BrowserModule } from "@angular/platform-browser";
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";
import { HomePage } from "../pages/home/home"; // import the page
import {HomePageModule} from "../pages/home/home.module"; // import the module

@NgModule({
  declarations: [
    MyApp,
  ],
  imports: [
    BrowserModule,
    IonicModule.forRoot(MyApp),
    HomePageModule // declare the module
  ],
  bootstrap: [IonicApp],
  entryComponents: [
    MyApp,
    HomePage, // declare the page
  ],
  providers: [
    StatusBar,
    SplashScreen,
    { provide: ErrorHandler, useClass: IonicErrorHandler },
  ]
})
export class AppModule {}

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

Solved it -- Component is part of the declaration of 2 modules

1. Remove pagename.module.ts file in app
2. Remove import { IonicApp } from 'ionic-angular'; in pagename.ts file
3. Remove @IonicPage() from pagename.ts file

And Run the command ionic cordova build android --prod --release its Working in my app

Had same problem. Just make sure to remove every occurrence of module in "declarations" but AppModule.

Worked for me.

Simple fix,

Go to your app.module.ts file and remove/comment everything that binds with add_event. There is no need of adding components to the App.module.ts which are generated by the ionic cli because it creates a separate module for components called components.module.ts.

It has the needed module component imports

As the error says to remove the module AddEvent from root if your Page/Component is already had ionic module file if not just remove it from the other/child page/component, at the end page/component should be present in only one module file imported if to be used.

Specifically, you should add in root module if required in multiple pages and if in specific pages keep it in only one page.

I accidentally created my own component with the same name as a library's component.

When I used my IDE to auto-import the library for the component, I chose the wrong library.

Therefore this error was complaining, that I was re-declaring the component.

I fixed by importing from my own component's code, instead of the library.

I could also fix by naming differently: avoid ambiguity.

In this scenario, create another shared module in that import all the component which is being used in multiple module.

In shared component. declare those component. And then import shared module in appmodule as well as in other module where you want to access. It will work 100% , I did this and got it working.

@NgModule({
    declarations: [HeaderComponent, NavigatorComponent],
    imports: [
        CommonModule, BrowserModule,
        AppRoutingModule,
        BrowserAnimationsModule,
        FormsModule,
    ] 
})
export class SharedmoduleModule { }
const routes: Routes = [
{
    path: 'Parent-child-relationship',
    children: [
         { path: '', component: HeaderComponent },
         { path: '', component: ParrentChildComponent }
    ]
}];
@NgModule({
    declarations: [ParrentChildComponent, HeaderComponent],
    imports: [ RouterModule.forRoot(routes), CommonModule, SharedmoduleModule ],
    exports: [RouterModule]
})
export class TutorialModule {
}
imports: [
    BrowserModule,
    AppRoutingModule,
    BrowserAnimationsModule,
    FormsModule,
    MatInputModule,
    MatButtonModule,
    MatSelectModule,
    MatIconModule,
    SharedmoduleModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }

I had the same error but I discovered that when you import an AddEventModule, you can't import an AddEvent module as it would present an error in this case.