Error: Cannot Determine The Module For Class Add Directive To The Ngmodule To Fix It

when i tried to build my ionic angular app i got this error:

[10:41:58]  Error: Cannot determine the module for class AutofocusDirective in
            directives/autofocus-directive.ts! Add
            AutofocusDirective to the NgModule to fix it. Cannot determine the module for class Elastic in
            directives/elastic-directive.ts! Add Elastic to
            the NgModule to fix it.

to fix it what i did was removed it form my directives directory because i was not using, after that, i was able to build my app for my web application.

this is the command i executed when i got the error: npm run build --prod