Doctrine 2 : Page, Block, Strategy pattern & related entity - php

Question

My problem is exactly that described in the Strategy Pattern article in Doctrine documentation :
A Page entity
A page can have some blocks
A block might be a text, an image, a form, a calendar, ... (strategy)
A page knows about blocks it contains, but doesn't know about their behaviours
Block inheritance is not possible
Described solution (Strategy pattern) seems exactly what I need (read article for further information) :
Page:
<?php
namespace Page\Entity;
class Page
{
/**
* #var int
* #Id #GeneratedValue
* #Column(type="integer")
*/
protected $id;
/**
* #var string
* #Column
*/
protected $title;
/**
* #var string
* #Column(type="text")
*/
protected $body;
/**
* #var Collection
* #OneToMany(targetEntity="Block", mappedBy="page")
*/
protected $blocks;
// ...
}
Block:
<?php
namespace Page\Entity;
class Block
{
/**
* #Id #GeneratedValue
* #Column(type="integer")
*/
protected $id;
/**
* #ManyToOne(targetEntity="Page", inversedBy="blocks")
*/
protected $page;
/**
* #Column
*/
protected $strategyClass;
/**
* Strategy object is instancied on postLoad by the BlockListener
*
* #var BlockStrategyInterface
*/
protected $strategyInstance;
// ...
}
Strategy interface:
<?php
namespace Page\BlockStrategy;
interface BlockStrategyInterface
{
public function setView($view);
public function getView();
public function setBlock(Block $block);
public function getBlock();
public function renderFrontend();
public function renderBackend();
}
I can easily imagine what would be my strategy if I would display a form or a calendar;
but what if my strategy is to display content of an other entity ?
The block needs to know about entity class/id and has to be deleted when related entity is removed.
I imagined to add entityClass and entityId properties in Block and load related entity on the postLoad event in a BlockListener.
But what if related entity doesn't exist ? I can't remove the block in postLoad.
So, I imagined to create an other listener watching for removal of related entity and remove refering Block in that listener.
But it means that I need to add a listener for every entity that can be put in a block.
It could work, but it seems very complicated... maybe someone has a better idea ?

Answer 1

I'm not sure if I understood well your question, but if what you want is to have entities inside entities and delete the child entities when the father is deleted, you could also treat the entity as a block and use a Composite pattern.
You basically could use the same interface on the entity and the blocks, and on the entity the display function could be something like:
foreach ($block in $blocks) {
$block->display();
}
For deleting all the children when you delete the parent entity, you could simply do it on the destructor of the entity.
function __destruct() {
foreach ($block in $blocks) {
/* call a common interface function that does all that need to be done, implemented on each block */
}
}
For more on Composite pattern:
http://en.wikipedia.org/wiki/Composite_pattern