How to use component in a in another module/router

Question

I'm trying to use another component from another module, but its not working in my router-outlet.

app.module

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { MainModule } from './main/main.module';
import { AppComponent } from './app/app.component';
import { KeypadComponent } from './keypad/keypad.component;
import { routing } from './app.routing';

@NgModule({
  declarations: [
    AppComponent,
    MainComponent,
    KeypadComponent
  ],
  imports: [
    BrowserModule,
    CommonModule,
    MainModule,
    routing
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

main.module

import { NgModule } from '@angular/core';
import { routing } from '../app.routing';

import { ProductComponent } from './product/product.component';

@NgModule({
  imports: [
    routing
  ],
  declarations: [ProductComponent]
})
export class MainModule { }

My issue is that when I try to call the Keypad Component in product.component.html , it will give me an error that says it does not exist. However, when I call it in my main.component.html , it works fine.

Answer 1

If your component should be used by app module and main module it should go in the main module or in another shared module. Following example show how to use a shared module.

AppModule declaration

@NgModule({
  declarations: [
    AppComponent,
    MainComponent,
  ],
  imports: [
    CommonModule,
    MainModule,
    SharedModule,
    routing
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

MainModule declaration

@NgModule({
  imports: [
    CommonModule,
    routing,
    SharedModule
  ],
  declarations: [ProductComponent]
})
export class MainModule { }

SharedModule declaration

@NgModule({
  imports: [ CommonModule ],
  declarations: [ KeypadComponent ],
  exports: [ KeypadComponent ]
})
export class SharedModule { }