codeigniter model error: Undefined property [duplicate]

You have to load the db library first. In autoload.php add :

$autoload['libraries'] = array('database');

Also, try renaming User model class for "User_model".

It solved throung second parameter in Model load:

$this->load->model('user','User');

first parameter is the model's filename, and second it defining the name of model to be used in the controller:

function alluser() 
{
$this->load->model('User');
$result = $this->User->showusers();
}

function user() { 

       parent::Model(); 

} 

=> class name is User, construct name is User.

function User() { 

       parent::Model(); 

}