Design patterns
Cadena de responsabilidad

Cadena de responsabilidad ejemplo (php)

Un método llamado en un objeto subirá la cadena de objetos hasta que se encuentre uno que pueda manejar la llamada correctamente. Este ejemplo particular utiliza experimentos científicos con funciones que solo pueden obtener el título del experimento, la identificación de los experimentos o el tejido utilizado en el experimento.

abstract class AbstractExperiment {
    abstract function getExperiment();
    abstract function getTitle();
}
 
class Experiment extends AbstractExperiment {
    private $experiment;
    private $tissue;
    function __construct($experiment_in) {
        $this->experiment = $experiment_in;
        $this->tissue = NULL;
    }
    function getExperiment() {
        return $this->experiment;
    }
    //this is the end of the chain - returns title or says there is none
    function getTissue() {
      if (NULL != $this->tissue) {
        return $this->tissue;
      } else {
        return 'there is no tissue applied';
      }
    }
}

class SubExperiment extends AbstractExperiment {
    private $experiment;
    private $parentExperiment;
    private $tissue;
    function __construct($experiment_in, Experiment $parentExperiment_in) {
      $this->experiment = $experiment_in;
      $this->parentExperiment = $parentExperiment_in;
      $this->tissue = NULL;
    }
    function getExperiment() {
      return $this->experiment;
    }
    function getParentExperiment() {
      return $this->parentExperiment;
    }   
    function getTissue() {
      if (NULL != $this->tissue) {
        return $this->tissue;
      } else {
        return $this->parentExperiment->getTissue();
      }
    }
}

//This class and all further sub classes work in the same way as SubExperiment above
class SubSubExperiment extends AbstractExperiment {
    private $experiment;
    private $parentExperiment;
    private $tissue;
    function __construct($experiment_in, Experiment $parentExperiment_in) { //as above }
    function getExperiment() { //same as above }
    function getParentExperiment() { //same as above }   
    function getTissue() { //same as above }
}