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                <?php  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                namespace Sonata\DoctrinePHPCRAdminBundle\Description;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Doctrine\Common\Persistence\ManagerRegistry;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use PHPCR\PathNotFoundException;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use PHPCR\Util\PathHelper;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Symfony\Cmf\Component\Resource\Description\Description;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Symfony\Cmf\Component\Resource\Description\DescriptionEnhancerInterface;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Symfony\Cmf\Component\Resource\Puli\Api\PuliResource;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Symfony\Cmf\Component\Resource\Repository\Resource\CmfResource;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * A description enhancer to add the position/sorting value of children on a parent.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @author Maximilian Berghoff <[email protected]>  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                 */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                class PositionEnhancer implements DescriptionEnhancerInterface  | 
            
            
                                                                        
                            
            
                                    
            
            
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                { | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @var \PHPCR\SessionInterface  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    private $session;  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @param ManagerRegistry $manager  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @param $sessionName  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function __construct(ManagerRegistry $manager, $sessionName)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $this->session = $manager->getConnection($sessionName);  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * {@inheritdoc} | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function enhance(Description $description)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $nodePath = $description->getResource()->getPath();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $nodeName = PathHelper::getNodeName($nodePath);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $parentPath = PathHelper::getParentPath($nodePath);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        try { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $parentNode = $this->session->getNode($parentPath);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        } catch (PathNotFoundException $exception) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            return false;  | 
            
                            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $nodeIterator = $parentNode->getNodes();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $nodeIterator->rewind();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $counter = 0;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        while ($nodeIterator->valid()) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ++$counter;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            if ($nodeIterator->key() === $nodeName) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                break;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $nodeIterator->next();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $description->set('position', $counter); | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * {@inheritdoc} | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function supports(PuliResource $resource)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        if (!$resource instanceof CmfResource) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            return false;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        try { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $parentNode = $this->session->getNode(PathHelper::getParentPath($resource->getPath()));  | 
            
                            
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                        } catch (PathNotFoundException $exception) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            return false;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        // Todo: check for non orderable type  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return true;  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                    }  | 
            
            
                                                        
            
                                    
            
            
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                }  | 
            
            
                                                        
            
                                    
            
            
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.