Invalid argument supplied for foreach() - codeigniter

Question

I do not understand how to fix this codes:
return $this->db->update('slideshow');
I have tried several codes like changing it to $query or $query_result etc. and the error still exist. I still have to use $this->db->update('');
controllers/Cuploadfile.php
function uploadedit()
{
$data['images'] = ''; // Need to place it here and get images here.
//set preferences
$config['upload_path'] = './uploads/';
$config['allowed_types'] = 'jpg|gif';
$config['max_size'] = '500000';
//load upload class library
$this->load->library('upload', $config);
$this->load->model('Mpages');
if (!$this->upload->do_upload('filename'))
{
// case - failure
$upload_error = array('error' => $this->upload->display_errors());
$this->load->view('addslideshows', $upload_error);
}
else
{
// case - success
$upload_data = $this->upload->data();
$filename = $upload_data['file_name'];
$image_id = $this->uri->segment(3);
$data['images'] = $this->Mpages->edit_slideshow($filename, $image_id);
$data['success_msg'] = '<div class="alert alert-success text-center">Your file <strong>' . $upload_data['file_name'] . '</strong> was successfully uploaded!</div>';
$this->load->view('editslideshows', $data);
}
}
models/Mpages.php
public function edit_slideshow($filename, $image_id)
{
$this->db->set('slideshow_image', $filename);
$this->db->where('image_id', $image_id);
return $this->db->update('slideshow');
}

Answer 1

Change your Model's function to this
public function edit_slideshow($filename, $image_id){
$this->db->where('image_id', $image_id);
$this->db->update('slideshow', $filename);
if($this->db->affected_rows() > 0){
return true;
}else{
return false;
}
}

Answer 2

rewrite your model
public function edit_slideshow($filename, $image_id)
{
$this->db->set('slideshow_image', $filename);
$this->db->where('image_id', $image_id);
$update=$this->db->update('slideshow');
if($update)
{
return true;
}
return false;
}