[eluser]Jilani Jidni[/eluser]
I think you have not load your database. you can do this this way when you attempt to load the model
Code:
$this->load->model('Designers_model', 'designer',TRUE);
if you pass TRUE into the third parameter this will automatic load the database by default settings. To know more please read the CodeIgniter user guide.
hope this will work for you.