Question

I struggle organising my code, and I would like to share my “problem” with you by using a simple example: the calculation of the area of a rectangle. I put the code for example, but reading the first intro on each class section explains the situation easily.

Entity Rectangle:

The entity Rectangle contains two inportant properties $length and $width.

// src/Acme/CalculationBundle/Entity/Rectangle.php

/**
 * @ORM\Entity(repositoryClass="Acme\CalculationBundle\Repository\RectangleRepository")
 * @ORM\Table(name="rectangle")
 */
class Rectangle
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="integer")
     */
    protected $length;

    /**
     * @ORM\Column(type="integer")
     */
    protected $width;

FORM

Of course, the user can set length and width via a form

CONTROLLER

CreateRectangleAction: renders the form on GET request and work on the data on a POST request.

ViewRectangleAction: shows the rectangle.

RECTANGLE MANAGER

Now, to make sure the controller doesn’t do too much stuff, I use a RectangleManager to realise common operation on Rectangle objects and use it as a service (injecting the appropriate elements).

// src/Acme/CalculationBundle/Entity/RectangleManager.php
use Doctrine\ORM\EntityManager;
use Doctrine\ORM\EntityRepository;
use Acme\EmployerBundle\Entity\Manager;

class rectangleManager
{
    /**
     * Doctrine entity manager
     * @var EntityManager
     */
    protected $em;

    /**
     * @var EntityRepository
     */
    protected $repository;

    /**
     * 
     * @var string
     */
    protected $class;

    public function __construct(EntityManager $em, $class)
    {
        $this->em = $em;
        $this->class = $class;
        $this->repository = $em->getRepository($class);
    }

    /**
     * @param $id
     * @return Rectangle
     */
    public function find($id)
    {
        $rectangle =  $this->repository->find($id);
    }

THE PROBLEM: WHAT IF?

What if I need to do some calculations on the rectangle? For example, if I need to add an area property so that I can render the area directly in the template without doing the calculation (length*width) in the template?

Not knowing how to do this properly, I went for this pretty bad solution:

I created a RectangleDisplay class (where I inject the rectangle entity) and display that entity instead of the Rectangle entity when calling ViewRectangleAction in the controller.

// src/Acme/CalculationBundle/Entity/
class RectangleDisplay
{
    /**
     * @var Rectangle $rectangle
     */
    protected $rectangle;

    /**
     * @var Integer 
     */
    protected $area;

    /**
     * @param Rectangle $rectangle
     */
    public function __construct(rectangle $rectangle){

        $this->rectangle = $rectangle;
        //calculate are
        $area = this->calculateArea($this->rectangle->getLength(),$this->rectangle->getWidth());
        $this->area = $area;

    }

    /**
     * @return Integer $area
     */
    public function calculateArea($length,$width)
    {
         return $length * $width;
    }

Now the property area is directly accessible in the template. In the case of a rectangle, that is fine, but in the case of a more complex element (cone, …), I might want to use a service that is crazy at doing calculation. I am not gonna inject the container in my RectangleDisplayEntity, am I?

Answer 1

This belongs in your entity.

class Rectangle
{
    // ...

    public function getArea()
    {
        return $this->length * $this->width;
    }
}

The area of a rectangle is a property of a rectangle. It’s not some crazy calculation that should be delegated to another service, and it’s especially not something display-related (though you may think that based on it being displayed in your application).

Now, if you were calculating something a lot more complex, it’s probably worth moving to a service / another class. (Services = verbs, Entities = nouns and their properties).