Codeigniter Call to a member function where() on bool

Question

I tried to set seen to any contact data in database, but when i try that:

public function showMessage($id){
        $this->load->model('Message_Model');
        $messageData = $this->Message_Model->selectMessage($id);
        if($messageData[0]->messageIsSeen == 0){
            $this->Message_Model->setSeenToMessage($id);        
        }
        $data = array('messageData' => $messageData[0]);
        $this->load->view('Back/MessageDetail', $data);
    }

Model:

function setSeenToMessage($id){
        $this->db->update('messages', array('messageIsSeen' => 1))->where('messageId', $id);
        return 1;
    }

It throws that error

Answer 1

i solved it like this change

function setSeenToMessage($id){
        $this->db
             ->where('messageId', $id);
             ->update('messages', array('messageIsSeen' => 1))

        return 1;
    }

nevertheless, still i don't know how did it works