Cannot determine the module for class X in X.ts! Add X to the NgModule to fix it error in ionic2

Question

I am facing an issue when I try to build my app using the following command :

ionic cordova run android --prod --release

Everything runs fine if

Answer 1

This could also be a filename casing problem. see https://github.com/angular/angular-cli/issues/10732

Answer 2

elaborating on answer by @[Thom Kiesewetter]

It could also be a path casing issue reference used in the module or in routes or anywhere else

e.g path was

import { EmployeeComponent } from "./Entities/employee.component";

instead of

import { EmployeeComponent } from "./entities/employee.component";

where the real path was "entities" and not "Entities"

Answer 3

Changed declarations to pages like below and it worked.

declarations: pages

I got the answer at :https://forum.ionicframework.com/t/error-while-running-the-ionic3-app-in-production-mode/106294

Answer 4

I had the same problem , but for me, two components with the same name were there something like below,

my-first-app\src\app\header\header.component.ts

my-first-app\src\header\header.component.ts

the second one is unused and wrongly placed as all my codes were inside my-first-app\src\app only. I removed the second one and it resolved my issue.