dk/calculator-bundle

Calculated entity properties for Symfony

DKCalculatorBundle

This is a simple bundle that allows you to use dynamically calculated properties in Doctrine entities., _(*1)

Installation

To install CalculatorBundle with Composer just add the following to your composer.json file:, _(*2)

// composer.json
{
    // ...
    require: {
        // ...
        "dk/calculator-bundle": "dev-master"
    }
}

Then, you can install the new dependencies by running Composer's update command from the directory where your composer.json file is located:, _(*3)

php composer.phar update dk/calculator-bundle

Now, Composer will automatically download all required files, and install them for you. All that is left to do is to update your AppKernel.php file, and register the new bundle:, _(*4)

<?php

// in AppKernel::registerBundles()
$bundles = array(
    // ...
    new DK\CalculatorBundle\DKCalculatorBundle(),
    // ...
);

Usage

Suppose you have a User entity, and a Transaction entity with a @ManyToOne association to User. Further suppose that you want to have a balance property on User which adds up all the user's transactions. It would be possible to do this using a bi-directional association and adding up the values in PHP, but this would be very inefficient compared to using DQL. It would also be possible to make a custom repository (or a custom service) that hydrates the entity by hand, but this means you need to access the entity in a special way and if you are using serialization (e.g. with https://github.com/schmittjoh/JMSSerializerBundle) this can get quite complicated., _(*5)

This bundle offers another solution:, _(*6)

use DK\CalculatorBundle\Annotation\Calculator;

/**
 * @ORM\Entity
 */
class User {

    /**
     * @Calculator(class="UserCalculator")
     */
    protected $balance;
    public function getBalance() { return $this->balance; }

    /**
     * @Calculator(service="my.calculator.service")
     */
    protected $serviceBalance;
    public function getServiceBalance() { return $this->serviceBalance; }

}

class UserCalculator {

    public function getBalance(User $user, EntityManager $em) {
        $query = $em->createQuery("SELECT SUM(t.value) FROM Transaction t JOIN t.user u WHERE u=:user");
        $query->setParameter('user', $user);
        return (float)$query->getSingleScalarResult();
    }

}

/**
 * @ORM\Entity
 */
class Transaction {

    /**
     * @ORM\Column(type="decimal", scale=2)
     * @JMS\Expose
     */
    protected $value;
    public function setValue($value) { $this->value = $value; return $this; }
    public function getValue() { return $this->value; }

    /**
     * @ORM\ManyToOne(targetEntity="User")
     */
    protected $user;
    public function setUser($value) { $this->user = $value; return $this; }
    public function getUser() { return $this->user; }

}

A class (any class will do) is specified in the class property of the @Calculator annotation, and when the entity has loaded a method name get<property>, is<property> or has<property> will be called on this class. The methods are passed the entity as a parameters, and when using class instead of service the EntityManager is passed as the second parameter., _(*7)

Future

This was knocked together very quickly and it can be extended and improved in many ways., _(*8)

• Caching: by specifying a calculated fields dependencies in the annotation we can store a value in the database and only perform new calculations when the dependencies change
• Unit tests