public function postEdit($id, ProductModel $product)
 {
     $validator = new Validation();
     $validator->setRule('required', $product->name, null, 'name');
     $validator->setRule('required', $product->description, null, 'description');
     $validator->setRule('required', $product->price, null, 'price');
     $validator->setRule('required', $product->quantity, null, 'quantity');
     $validator->setRule('required', $product->category_id, null, 'category');
     $validator->setRule('numeric', $product->quantity, null, 'quantity');
     $validator->setRule('numeric', $product->price, null, 'price');
     if (!$validator->validate()) {
         Session::setError($validator->getErrors()[0]);
         Redirect::back();
     }
     if ($this->product->edit($id, $product->name, $product->description, $product->price, $product->quantity, $product->category_id) !== 1) {
         Session::setError('something went wrong');
         Redirect::back();
     }
     Session::setMessage('done');
     Redirect::to('');
 }