set_value() not working for hidden fields?

[eluser]Sein Kraft[/eluser]
[quote author="InsiteFX" date="1305456460"]You riles are wrong!
The secod category should be upper case...

Code:

$this->form_validation->set_rules('category', 'Category', 'trim|required|is_natural');

InsiteFX[/quote]
PFffffff!!!

My rules aren't wrong. Why people don't read the doncumentation before appear screaming and saying that everything is wrong because it isn't in upper case...

The second argument will be passed as text in the error message to be interpreted by the final user.

User Guide