CakePHP access uploaded file after validation - cakephp

Question

I have a field 'screenshot' that when I try to access in beforeSave callback the field it's empty.
The thing I do is access the $data on the beforeMarshal callback and store the array
into a model setting, then I can access that in the beforeSave and set 'screenshot' field to filename.ext if move_uploaded_file is true.
This is the current code:
Model
// Using CakePHP 3.8.5
public function validationDefault(Validator $validator)
{
$validator
->allowEmptyFile('screenshot', 'update')
->uploadedFile('screenshot' , [
'types' => ['image/jpeg', 'image/jpg', 'image/pjpeg'],
'maxSize' => 1000000 // 1MB
]);
return $validator;
}
public function beforeMarshal(Event $event, ArrayObject $data, ArrayObject $options)
{
if (isset($data['screenshot']) && $data['screenshot']['error'] === UPLOAD_ERR_OK) {
$this->config([ 'file_array' => $data['screenshot'] ])
}
}
public function beforeSave(Event $event, EntityInterface $entity, ArrayObject $options)
{
...
$file = $this->config([ 'file_array');
if (move_uploaded_file($file['tmp_name'], $file_path)) {
return true;
} else {
throw new Exception(__('Unable to move...'));
}
}
Form
<?= $this->Form->create($project, ['type' => 'file']) ?>
<?= $this->Form->control('screenshot', ['type' => 'file', 'class' => 'form-control-file']) ?>
<?= $this->Form->button(__('Submit'), ['class' => 'btn btn-primary col-md-3 offset-md-9']) ?>
<?= $this->Form->end() ?>
The code I expected to work
public function validationDefault(Validator $validator)
{
$validator
->allowEmptyFile('screenshot', 'update')
->uploadedFile('screenshot' , [
'types' => ['image/jpeg', 'image/jpg', 'image/pjpeg'],
'maxSize' => 1000000 // 1MB
]);
return $validator;
}
public function beforeSave(Event $event, EntityInterface $entity, ArrayObject $options)
{
...
$file = $entity->screenshot; // this is empty
if (move_uploaded_file($file['tmp_name'], $file_path)) {
return true;
} else {
throw new Exception(__('Unable to move...'));
}
}
Why is $entity->screenshot empty on BeforeSave?
Is this the correct way to do this?

Answer 1

At marshalling time (when patching/creating entities), CakePHP will cast/convert the input according to the database types mapped for the fields.
For your database field screenshot, which is VARCHAR, that would be \Cake\Database\Type\StringType, which returns an empty string for arrays. The reasoning being that the marshalling stage shouldn't cause "crashes", but ideally create entities with data compatible to the respective database types, which can finally be validated via application rules if necessary, for which the errors can be as easily presented to the user as the ones for the validation rules.
The two most popular ways to handle this IMHO are:
Using a different field name for the upload, one that isn't mapped to an existing database column, eg something like screenshot_upload
Using a custom database type for the field, one that doesn't transform the array
Personally I prefer the former.