Codeigniter Active Records Fatal Error - php

Question

new to stack overflow (and codeigniter!) and I'm running into this issue on my first project, naturally... I'm sure its a bonehead error on my part, but I've been researching and trying to figure it out for the last few hours and I cat seem to figure it out...
I have the database library autoloaded, but everytime I try to use the methods in my model I get this error:
"Fatal error: Call to a member function where() on a non-object in application\models\user_model.php on line 13"
this is my User controller method called by the form action from my login form view:
function login() {
$this->load->model('user_model');
$query = $this->user_model->validate();
if ($query)
{
$data = array(
'username' => $this->input->post('username'),
'is_logged_in' => true
);
$this->session->set_userdata($data);
redirect('members');
}
else
{
$this->load->view('user');
}
} // end login function
this is my model:
<?php
class User_model extends CI_Model {
function __construct() {
parent::__construct();
}
// -------------------------------------------------------------------------------
// validate(): query db for user/pass and return true or false
function validate() {
$this->db->where('username', $this->input->post('username'));
$this->db->where('password', sha1($this->input->post('password')));
$query = $this->db->get('users');
if ($query->num_rows() > 0)
{
return true;
}
} // end validate function
// -------------------------------------------------------------------------------
function check()
{
$dbo = $this->load->database('default',TRUE);
$query = $this->$dbo->get('users');
echo $query->num_rows();
}
} // end user_model class
when I was attempting to debug the issue, I added the db methods to the controller and they worked fine... when using them in my model they dont want to work for whatever reason and throw the fatal error I mentioned. Appreciate any help you guys can throw my way.
Thanks in advance!
(using codeigniter 2.1)
EDIT:
Just to clear things up a little bit more, When I add the validate method (from my model) to my controller, I get no errors, and everything works fine... But when leaving it in the model and calling it from the controller I get the fatal error

Answer 1

You missed $query = part, Should be:
$query = $this->db->get('users');
if ($query->num_rows() > 0)
{
return true;
}
Edited:
I think you have not added all the parent constructor, try:
class Users extends CI_Model {
function __Users() {
parent::__CI_Model();
$this->load->database();
}

Answer 2

I think the function validate in your model should be like this
// validate(): query db for user/pass and return true or false
function validate($username,$password) {
$this->db->where('username', $username);
$this->db->where('password', sha1($password));
$query = $this->db->get('users');
if ($query->num_rows() > 0)
{
return true;
}
} // end validate function
In your controller you can call it like so
function login()
{
$query =$this->user_model->validate($this->input->post('username'),$this->input->post('password'));
// the rest
}