What is the difference between trait and behavior in cakephp 3? - behavior

Question

I find soft delete in cakephp 3 that implemented via traits. And I try to implement it via behaviors. But unlike the trait version, SoftDeleteBehavior do not work.
I have this line in my model initialize method:
$this->addBehavior('SoftDelete');
And this is my SoftDeleteBehavior
namespace App\Model\Behavior;
use Cake\ORM\Behavior;
use Cake\ORM\RulesChecker;
use Cake\Datasource\EntityInterface;
use App\Model\Behavior\MyQuery;
class SoftDeleteBehavior extends Behavior {
public $user_id = 1;
public function getDeleteDate() {
return isset($this->deleteDate) ? $this->deleteDate : 'deleted';
}
public function getDeleter() {
return isset($this->deleter) ? $this->deleter : 'deleter_id';
}
public function query() {
return new MyQuery($this->connection(), $this);
}
/**
* Perform the delete operation.
*
* Will soft delete the entity provided. Will remove rows from any
* dependent associations, and clear out join tables for BelongsToMany associations.
*
* #param \Cake\DataSource\EntityInterface $entity The entity to soft delete.
* #param \ArrayObject $options The options for the delete.
* #throws \InvalidArgumentException if there are no primary key values of the
* passed entity
* #return bool success
*/
protected function _processDelete($entity, $options) {
if ($entity->isNew()) {
return false;
}
$primaryKey = (array)$this->primaryKey();
if (!$entity->has($primaryKey)) {
$msg = 'Deleting requires all primary key values.';
throw new \InvalidArgumentException($msg);
}
if (isset($options['checkRules']) && !$this->checkRules($entity, RulesChecker::DELETE, $options)) {
return false;
}
$event = $this->dispatchEvent('Model.beforeDelete', [
'entity' => $entity,
'options' => $options
]);
if ($event->isStopped()) {
return $event->result;
}
$this->_associations->cascadeDelete(
$entity,
['_primary' => false] + $options->getArrayCopy()
);
$query = $this->query();
$conditions = (array)$entity->extract($primaryKey);
$statement = $query->update()
->set([$this->getDeleteDate() => date('Y-m-d H:i:s') , $this->getDeleter() => $this->user_id])
->where($conditions)
->execute();
$success = $statement->rowCount() > 0;
if (!$success) {
return $success;
}
$this->dispatchEvent('Model.afterDelete', [
'entity' => $entity,
'options' => $options
]);
return $success;
}
If I use trait, SoftDeleteTrait works in true manner. But SoftDeleteBehavior do not work properly!

Answer 1

One is a PHP language construct, the other is a programmatic concept. You may want to read upon what traits are, so that you understand that this question, as it stands, doesn't make too much sense. Also stuff like "doesn't work" doesn't serve as a proper problem description, please be more specific in the future.
That being said, CakePHP behaviors do serve the purpose of horizontal code reuse, similar to traits, as opposed to vertical reuse by inheritance.
However, even if they have conceptual similarities, you cannot simply exchange them as you seem to do in your code, a trait will be composited into the class on which it is used, so that it becomes part of it as if it were written directly in the class definition, and therefore has the ability to overwrite inherited code like the Table::_processDelete() method, a behavior on the other hand is a totally independent class, which is being instantiated and injected as a dependency into a table class at runtime, and calls to its methods are being delegated via the table class (see Table::__call()), unless a method with the same name already exists on the table class, which in your case means that _processDelete() will never be invoked.
I'd suggest that you study a little more on PHP/OOP basics, as this is rather basic stuff that can be untangled easily by just having a look at the source. Being able to understand how the CakePHP code base and the used concepts do work will make your life much easier.