Fetch single Data From Database and display in Codeigniter

I have to fetch single Data From Database and display it in text box in Codeigniter.Please check the code and assist me where am i wrong?

Controller

public function update_retrive()

{

$id = $this->uri->segment(3);

$this->load->model("model_add_user");

$d=$this->model_add_user->update_retrive($id);

$data['posts'] = $d;

}

Model

public function update_retrive($userId)

{

$this->db->where('userId',$userId);

$this->db->from('add_user');

$q = $this->db->get();

return $q;

}

View

foreach ($posts->result() as $post)

{