71 lines
2.3 KiB
ReStructuredText
71 lines
2.3 KiB
ReStructuredText
Implementing the Notify ChangeTracking Policy
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=============================================
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The NOTIFY change-tracking policy is the most effective
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change-tracking policy provided by Doctrine but it requires some
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boilerplate code. This recipe will show you how this boilerplate
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code should look like. We will implement it on a
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`Layer Supertype <http://martinfowler.com/eaaCatalog/layerSupertype.html>`_
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for all our domain objects.
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Implementing NotifyPropertyChanged
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----------------------------------
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The NOTIFY policy is based on the assumption that the entities
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notify interested listeners of changes to their properties. For
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that purpose, a class that wants to use this policy needs to
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implement the ``NotifyPropertyChanged`` interface from the
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``Doctrine\Common`` namespace.
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::
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<?php
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use Doctrine\Common\NotifyPropertyChanged,
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Doctrine\Common\PropertyChangedListener;
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abstract class DomainObject implements NotifyPropertyChanged
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{
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private $_listeners = array();
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public function addPropertyChangedListener(PropertyChangedListener $listener) {
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$this->_listeners[] = $listener;
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}
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/** Notifies listeners of a change. */
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protected function _onPropertyChanged($propName, $oldValue, $newValue) {
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if ($this->_listeners) {
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foreach ($this->_listeners as $listener) {
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$listener->propertyChanged($this, $propName, $oldValue, $newValue);
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}
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}
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}
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}
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Then, in each property setter of concrete, derived domain classes,
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you need to invoke \_onPropertyChanged as follows to notify
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listeners:
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::
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<?php
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// Mapping not shown, either in annotations, xml or yaml as usual
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class MyEntity extends DomainObject
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{
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private $data;
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// ... other fields as usual
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public function setData($data) {
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if ($data != $this->data) { // check: is it actually modified?
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$this->_onPropertyChanged('data', $this->data, $data);
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$this->data = $data;
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}
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}
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}
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The check whether the new value is different from the old one is
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not mandatory but recommended. That way you can avoid unnecessary
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updates and also have full control over when you consider a
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property changed.
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