Understanding and Applying Polymorphism in PHP

gistfile1.txt

/*

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

*/

interface MyInterface {
    // methods
}

class MyClass implements MyInterface {
    // methods
}

interface MyInterface {
    public function doThis();
    public function doThat();
    public function setName($name);
}

// VALID
class MyClass implements MyInterface {
    protected $name;
    public function doThis() {
        // code that does this
    }
    public function doThat() {
        // code that does that
    }
    public function setName($name) {
        $this->name = $name;
    }
}
 
// INVALID
class MyClass implements MyInterface {
    // missing doThis()!
 
    private function doThat() {
        // this should be public!
    }
    public function setName() {
        // missing the name argument!
    }
}

abstract class MyAbstract {
    // methods
}

class MyClass extends MyAbstract {
    // class methods
}

abstract class MyAbstract {
    public $name;
    public function doThis() {
        // do this
    }
    abstract public function doThat();
    abstract public function setName($name);
}

class poly_base_Article {
    public $title;
    public $author;
    public $date;
    public $category;
 
    public function  __construct($title, $author, $date, $category = 0) {
        $this->title = $title;
        $this->author = $author;
        $this->date = $date;
        $this->category = $category;
    }
}

class poly_base_Article {
    //...
    public function write($type) {
        $ret = '';
        switch($type) {
            case 'XML':
                $ret = '<article>';
                $ret .= '<title>' . $obj->title . '</title>';
                $ret .= '<author>' . $obj->author . '</author>';
                $ret .= '<date>' . $obj->date . '</date>';
                $ret .= '<category>' . $obj->category . '</category>';
                $ret .= '</article>';
                break;
            case 'JSON':
                $array = array('article' => $obj);
                $ret = json_encode($array);
                break;
        }
        return $ret;
    }
}

interface poly_writer_Writer {
    public function write(poly_base_Article $obj);
}

class poly_writer_XMLWriter implements poly_writer_Writer {
    public function write(poly_base_Article $obj) {
        $ret = '<article>';
        $ret .= '<title>' . $obj->title . '</title>';
        $ret .= '<author>' . $obj->author . '</author>';
        $ret .= '<date>' . $obj->date . '</date>';
        $ret .= '<category>' . $obj->category . '</category>';
        $ret .= '</article>';
        return $ret;
    }
}

class poly_writer_JSONWriter implements poly_writer_Writer {
    public function write(poly_base_Article $obj) {
        $array = array('article' => $obj);
        return json_encode($array);
    }
}

class poly_base_Article {
    //...
    public function write(poly_writer_Writer $writer) {
        return $writer->write($this);
    }
}

class poly_base_Factory {
    public static function getWriter() {
        // grab request variable
        $format = $_REQUEST['format'];
        // construct our class name and check its existence
        $class = 'poly_writer_' . $format . 'Writer';
        if(class_exists($class)) {
            // return a new Writer object
            return new $class();
        }
        // otherwise we fail
        throw new Exception('Unsupported format');
    }
}

$article = new poly_base_Article('Polymorphism', 'Steve', time(), 0);
 
try {
    $writer = poly_base_Factory::getWriter();
}
catch (Exception $e) {
    $writer = new poly_writer_XMLWriter();
}
 
echo $article->write($writer);