Design patterns
Ansvarskedja

Exempel på kedjan av ansvar (php)

En metod som kallas i ett objekt kommer att flytta upp objektkedjan tills en hittas som kan hantera samtalet ordentligt. Detta specifika exempel använder vetenskapliga experiment med funktioner som bara kan få titeln på experimentet, experimentens id eller vävnaden som används i experimentet.

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 }
}