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Implementing the Notify ChangeTracking Policy
The NOTIFY change-tracking policy is the most effective change-tracking policy provided by Doctrine but it requires some boilerplate code. This recipe will show you how this boilerplate code should look like. We will implement it on a Layer Supertype for all our domain objects.
Implementing NotifyPropertyChanged
The NOTIFY policy is based on the assumption that the entities
notify interested listeners of changes to their properties. For
that purpose, a class that wants to use this policy needs to
implement the NotifyPropertyChanged interface from the
Doctrine\Common namespace.
1 <?php
use Doctrine\Common\NotifyPropertyChanged,
Doctrine\Common\PropertyChangedListener;
abstract class DomainObject implements NotifyPropertyChanged
{
private $_listeners = [];
public function addPropertyChangedListener(PropertyChangedListener $listener): void
{
$this->_listeners[] = $listener;
}
/** Notifies listeners of a change. */
protected function _onPropertyChanged($propName, $oldValue, $newValue): void
{
if (!empty($this->_listeners)) {
foreach ($this->_listeners as $listener) {
$listener->propertyChanged($this, $propName, $oldValue, $newValue);
}
}
}
} 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Then, in each property setter of concrete, derived domain classes, you need to invoke _onPropertyChanged as follows to notify listeners:
1 <?php
// Mapping not shown, either in annotations or xml as usual
class MyEntity extends DomainObject
{
private $data;
// ... other fields as usual
public function setData($data): void
{
if ($data != $this->data) { // check: is it actually modified?
$this->_onPropertyChanged('data', $this->data, $data);
$this->data = $data;
}
}
} 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
The check whether the new value is different from the old one is not mandatory but recommended. That way you can avoid unnecessary updates and also have full control over when you consider a property changed.