| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  | namespace Scriptotek\Alma\Bibs; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  | use Danmichaelo\QuiteSimpleXMLElement\QuiteSimpleXMLElement; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  | use Scriptotek\Alma\Client; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  | use Scriptotek\Alma\Model\LazyResource; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  | use Scriptotek\Marc\Record as MarcRecord; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  | /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  |  * A single Holding resource. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  |  */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  | class Holding extends LazyResource | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |     /* @var string */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  |     public $holding_id; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |     /* @var Bib */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |     public $bib; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  |     /* @var Items */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 22 |  |  |     public $items; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 23 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 24 |  |  |     /* @var MarcRecord */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 25 |  |  |     protected $_marc; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 26 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |     public function __construct(Client $client, Bib $bib, $holding_id) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |         parent::__construct($client); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |         $this->bib = $bib; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  |         $this->holding_id = $holding_id; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |         $this->items = Items::make($this->client, $bib, $this); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  |      * Get the model data. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |     protected function fetchData() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 |  |  |         return $this->client->getXML($this->url()); | 
                            
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                | 41 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |      * Check if we have the full representation of our data object. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 |  |  |      * @param $data | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |      * @return bool | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |     protected function isInitialized($data) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |         return is_a($data, QuiteSimpleXMLElement::class) && $data->has('record'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 |  |  |      * Update the MARC record on this holding object. Chainable method. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 |  |  |      * @param string $xml | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 60 |  |  |      * @return Holding | 
            
                                                                                                            
                            
            
                                    
            
            
                | 61 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 62 |  |  |     public function setMarcRecord($xml) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 63 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 64 |  |  |         $this->_marc = MarcRecord::fromString($xml); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 65 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 66 |  |  |         return $this; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 67 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 68 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 69 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 70 |  |  |      * Called when data is available to be processed. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 71 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 72 |  |  |      * @param mixed $data | 
            
                                                                                                            
                            
            
                                    
            
            
                | 73 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 74 |  |  |     protected function onData($data) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 75 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 76 |  |  |         $this->setMarcRecord($data->first('record')->asXML()); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 77 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 78 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 79 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 80 |  |  |      * Generate the base URL for this resource. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 81 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 82 |  |  |      * @return string | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 83 |  |  |      */ | 
            
                                                                        
                            
            
                                    
            
            
                | 84 |  |  |     protected function urlBase() | 
            
                                                                        
                            
            
                                    
            
            
                | 85 |  |  |     { | 
            
                                                                        
                            
            
                                    
            
            
                | 86 |  |  |         return "/bibs/{$this->bib->mms_id}/holdings/{$this->holding_id}"; | 
            
                                                                        
                            
            
                                    
            
            
                | 87 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 88 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 89 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 90 |  |  |      * Get the MARC record for this holding object. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 91 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 92 |  |  |     public function getRecord() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 93 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 94 |  |  |         return $this->init()->_marc; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 95 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 96 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 97 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 98 |  |  |      * Get the items for this holding. | 
            
                                                                                                            
                            
            
                                    
            
            
                | 99 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 100 |  |  |     public function getItems() | 
            
                                                                                                            
                            
            
                                    
            
            
                | 101 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 102 |  |  |         return $this->items; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 103 |  |  |     } | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 104 |  |  | } | 
            
                                                        
            
                                    
            
            
                | 105 |  |  |  | 
            
                        
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.