form validation on detail screen

Hi,

I have a detail screen, and I'm trying to implement form validation on it as described in 
https://www.codeigniter.com/userguide3/l...ation.html


This works fine for simple having a create screen , where no data is available from the database yet.

However, ideally I would like to reuse the same screen for editing, which means it has to retrieve data from the database.

I know how to get data from the database and display it on the screen, and I know how to show the validated screen, but I'm trying to get the combination of both to work :

1) Should get data from the database on it's values from the database
2) After adapting the screen, it should validate the screen, filling in the incorrect values while leaving the correct values

What is the best practice to deal with this behavior ? A simple example of a editing screen would suffice.

Thanks.