General Polymorphism with PHP examples

Question

As only Dogs can play \"fetch\", is this example a good or a bad idea? I suspect it\'s a really bad idea due to the usage of instanceof, but I\'m not entirely sure why.

Answer 1

Almost the same as you Krishnadas, Brad. This article helped me alot in understanding how to handle polymorphism in PHP

http://code.tutsplus.com/tutorials/understanding-and-applying-polymorphism-in-php--net-14362

interface shape_drawer{
    public function draw(Shape $obj);
}

class circle implements shape_drawer{
    public function draw(Shape $obj){
        echo "Drawing Circle, Area: {$obj->area} 
";
    }
}

class square implements shape_drawer{
    public function draw(Shape $obj){
        echo "Drawing Square, Area: {$obj->area} 
";
    }
}

class triangle implements shape_drawer{
    public function draw(Shape $obj){
        echo "Drawing Triangle, Area: {$obj->area} 
";
    }    
}

class shape_factory{
    public static function getShape(){

        $shape = $_REQUEST['shape'];

        if(class_exists($shape)) {
            return new $shape();
        }
        throw new Exception('Unsupported format');
    }
}

class Shape{

    public function __construct($area){
        $this->area = $area;
    }
    public function draw(shape_drawer $obj) {
        return $obj->draw($this);
    }
}


$shape = new Shape(50);
try {
    $drawer = shape_factory::getShape();
}
catch (Exception $e) {
    $drawer = new circle();
}

echo $shape->draw($drawer);