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                <?php  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * File containing the eZ\Publish\Core\Repository\Values\Content\Location class.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @copyright Copyright (C) eZ Systems AS. All rights reserved.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @license For full copyright and license information view LICENSE file distributed with this source code.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                namespace eZ\Publish\Core\Repository\Values\Content;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Closure;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\API\Repository\Values\Content\Location as APILocation;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\API\Repository\Values\Content\LocationList;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\Core\Repository\LocationListFactory\ChildrenLazySearchQuery;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\Core\Repository\TreeAccessor\TreeDelegate;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * This class represents a location in the repository.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @internal Meant for internal use by Repository, type hint against API object instead.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                class Location extends APILocation  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Content info of the content object of this location.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @var \eZ\Publish\API\Repository\Values\Content\ContentInfo  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected $contentInfo;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /** @var array */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected $path;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /** @var \eZ\Publish\Core\Repository\TreeAccessor\TreeDelegate */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    private $treeDelegate;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Returns the content info of the content object of this location.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return \eZ\Publish\API\Repository\Values\Content\ContentInfo  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function getContentInfo()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $this->contentInfo;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Function where list of properties are returned.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Override to add dynamic properties  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @uses \parent::getProperties()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param array $dynamicProperties  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return array  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected function getProperties($dynamicProperties = ['contentId'])  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return parent::getProperties($dynamicProperties);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Magic getter for retrieving convenience properties.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param string $property The name of the property to retrieve  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return mixed  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function __get($property)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        switch ($property) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            case 'contentId':  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                return $this->contentInfo->id;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            case 'path':  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                if ($this->path !== null) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                    return $this->path;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                if (isset($this->pathString[1]) && $this->pathString[0] === '/') { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                    return $this->path = explode('/', trim($this->pathString, '/')); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                return $this->path = [];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return parent::__get($property);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Magic isset for signaling existence of convenience properties.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param string $property  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return bool  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                     */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    public function __isset($property)  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    { | 
            
            
                                                                        
                            
            
                                    
            
            
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                        if ($property === 'contentId' || $property === 'path') { | 
            
            
                                                                        
                            
            
                                    
            
            
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                            return true;  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        return parent::__isset($property);  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function getChildren(): iterable  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $this->treeDelegate->getChildren($this);  | 
            
                            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function getSiblings(): iterable  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $this->treeDelegate->getSiblings($this);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function getAncestors(): iterable  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $this->treeDelegate->getAncestors($this);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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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.