Ionic 4 - Ionic Input Two-Way Binding

Please keep in mind to add the FormsModule to your module or create a SharedModule to import and export FormsModule

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    IonicModule,
    RouterModule.forChild([
      {
        path: '',
        component: HomePage
      }
    ])
  ],
  declarations: [HomePage]
})
export class HomePageModule { }

Ionic 3/4 with angular 6

In order to be able to use two-way data binding for form inputs you need to import the FormsModule package in your Angular module. For more info see the Angular official tutorial here

For Example

import { FormsModule } from '@angular/forms';

[...]

@NgModule({
  imports: [
    [...]
    FormsModule
  ],
  [...]
})