| 1 |  |  | <?php | 
            
                                                                                                            
                            
            
                                    
            
            
                | 2 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 3 |  |  | namespace CultuurNet\UDB3\Offer\Commands; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 4 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 5 |  |  | use CultuurNet\Deserializer\DeserializerInterface; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 6 |  |  | use CultuurNet\Deserializer\JSONDeserializer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 7 |  |  | use CultuurNet\Deserializer\MissingValueException; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 8 |  |  | use CultuurNet\Deserializer\NotWellFormedException; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 9 |  |  | use CultuurNet\UDB3\Label; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 10 |  |  | use CultuurNet\UDB3\Offer\OfferIdentifierCollection; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 11 |  |  | use ValueObjects\String\String; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 12 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 13 |  |  | class AddLabelToMultipleJSONDeserializer extends JSONDeserializer | 
            
                                                                                                            
                            
            
                                    
            
            
                | 14 |  |  | { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 15 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 16 |  |  |      * @var DeserializerInterface | 
            
                                                                                                            
                            
            
                                    
            
            
                | 17 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 18 |  |  |     private $offerIdentifierDeserializer; | 
            
                                                                                                            
                            
            
                                    
            
            
                | 19 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 20 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 21 |  |  |      * @param DeserializerInterface $offerIdentifierDeserializer | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 22 |  |  |      */ | 
            
                                                                        
                            
            
                                    
            
            
                | 23 |  |  |     public function __construct(DeserializerInterface $offerIdentifierDeserializer) | 
            
                                                                        
                            
            
                                    
            
            
                | 24 |  |  |     { | 
            
                                                                        
                            
            
                                    
            
            
                | 25 |  |  |         $this->offerIdentifierDeserializer = $offerIdentifierDeserializer; | 
            
                                                                        
                            
            
                                    
            
            
                | 26 |  |  |     } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 27 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 28 |  |  |     /** | 
            
                                                                                                            
                            
            
                                    
            
            
                | 29 |  |  |      * @param \ValueObjects\String\String $data | 
            
                                                                                                            
                            
            
                                    
            
            
                | 30 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 31 |  |  |      * @return AddLabelToMultiple | 
            
                                                                                                            
                            
            
                                    
            
            
                | 32 |  |  |      * | 
            
                                                                                                            
                            
            
                                    
            
            
                | 33 |  |  |      * @throws NotWellFormedException | 
            
                                                                                                            
                            
            
                                    
            
            
                | 34 |  |  |      */ | 
            
                                                                                                            
                            
            
                                    
            
            
                | 35 |  |  |     public function deserialize(String $data) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 36 |  |  |     { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 37 |  |  |         $data = parent::deserialize($data); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 38 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 39 |  |  |         if (empty($data->label)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 40 |  |  |             throw new MissingValueException('Missing value "label".'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 41 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 42 |  |  |         if (empty($data->offers)) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 43 |  |  |             throw new MissingValueException('Missing value "offers".'); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 44 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 45 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 46 |  |  |         $label = new Label($data->label); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 47 |  |  |         $offers = new OfferIdentifierCollection(); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 48 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 49 |  |  |         foreach ($data->offers as $offer) { | 
            
                                                                                                            
                            
            
                                    
            
            
                | 50 |  |  |             $offers = $offers->with( | 
            
                                                                                                            
                            
            
                                    
            
            
                | 51 |  |  |                 $this->offerIdentifierDeserializer->deserialize( | 
            
                                                                                                            
                            
            
                                    
            
            
                | 52 |  |  |                     new String( | 
            
                                                                                                            
                            
            
                                    
            
            
                | 53 |  |  |                         json_encode($offer) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 54 |  |  |                     ) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 55 |  |  |                 ) | 
            
                                                                                                            
                            
            
                                    
            
            
                | 56 |  |  |             ); | 
            
                                                                                                            
                            
            
                                    
            
            
                | 57 |  |  |         } | 
            
                                                                                                            
                            
            
                                    
            
            
                | 58 |  |  |  | 
            
                                                                                                            
                            
            
                                    
            
            
                | 59 |  |  |         return new AddLabelToMultiple($offers, $label); | 
                            
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                | 60 |  |  |     } | 
            
                                                                                                            
                                                                
            
                                    
            
            
                | 61 |  |  | } | 
            
                                                        
            
                                    
            
            
                | 62 |  |  |  | 
            
                        
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.