title: Where does Edit text validation happens in VIPER architecture ( Android )
body: <p>I read couple of articles regarding VIPER. So using the knowledge i got from it, i have build an sample app using viper architecture for my login Activity. In this activity i have 2 Edittexts (username and password) and one button. Once the user click the login button i need to validate the username and password if its not null, if it is null i should show an error message asking the user to input data.</p>
  <p>My question is, where can I put my Editext validation code?</p>
  <p>Which VIPER module handles that job?</p>