Extends a PHP class and it's children

Question

In one of my projects, I use an external library providing two classes : DrawingImage and DrawingCharset , both of them extending BaseDrawing .

I want to extends BaseDrawing to add some properties and alter an existsing method. But I also want theses modifications in "copy" of existing children ( DrawingImage and DrawingCharset ).

There is a simple way to do it ? Extending don't seems to be a solution : I must duplicate code between each subclass. And I'm not sure i can call a parent method through Trait.

Answer 1

Traits can access properties and methods of superclasses just like the subclasses that import them, so you can definitely add new functionality across children of BaseDrawing with traits.

<?php
class BaseDrawing
{
    public $baseProp;

    public function __construct($baseProp)
    {
        $this->baseProp = $baseProp;
    }

    public function doSomething()
    {
        echo 'BaseDrawing: '.$this->baseProp.PHP_EOL;
    }
}

class DrawingImage extends BaseDrawing
{
    public $drawingProp;

    public function __construct($baseProp, $drawingProp)
    {
        parent::__construct($baseProp);
        $this->drawingProp = $drawingProp;
    }

    public function doSomething()
    {
        echo 'DrawingImage: '.$this->baseProp.' - '.$this->drawingProp.PHP_EOL;
    }
}

class DrawingCharset extends BaseDrawing
{
    public $charsetProp;

    public function __construct($baseProp, $charsetProp)
    {
        parent::__construct($baseProp);
        $this->charsetProp = $charsetProp;
    }

    public function doSomething()
    {
        echo 'DrawingCharset: '.$this->baseProp.' - '.$this->charsetProp.PHP_EOL;
    }
}

/**
 * Trait BaseDrawingEnhancements
 * Adds new functionality to BaseDrawing classes
 */
trait BaseDrawingEnhancements
{
    public $traitProp;

    public function setTraitProp($traitProp)
    {
        $this->traitProp = $traitProp;
    }

    public function doNewThing()
    {
        echo 'BaseDrawingEnhancements: '.$this->baseProp.' - '.$this->traitProp.PHP_EOL;
    }
}

class MyDrawingImageImpl extends DrawingImage
{
    // Add the trait to our subclass
    use BaseDrawingEnhancements;
}

class MyDrawingCharsetImpl extends DrawingCharset
{
    // Add the trait to our subclass
    use BaseDrawingEnhancements;
}

$myDrawingImageImpl = new MyDrawingImageImpl('Foo', 'Bar');
$myDrawingImageImpl->setTraitProp('Wombats');

$myDrawingCharsetImpl = new MyDrawingCharsetImpl('Bob', 'Alice');
$myDrawingCharsetImpl->setTraitProp('Koalas');

$myDrawingImageImpl->doSomething();
$myDrawingCharsetImpl->doSomething();

$myDrawingImageImpl->doNewThing();
$myDrawingCharsetImpl->doNewThing();