Symfony2 - Problems with Doctrine2 Preupdate

Question

My entity Budget has some methods that are executed in PrePersist and PreUpdate. It’s them:

/**
 * @return \DateTime
 */
public function generateNextPaymentDate()
{
    if ($this->getStartsAt() !== null) {
        $date = new \DateTime($this->getStartsAt()->format('Y-m-d'));
        return $date->add(new \DateInterval('P' . $this->getCheckFor() . 'D'));
    }
}

/**
 * @return decimal
 */
public function calculateTotalBudgetPrice()
{
    $totalBudgetPrice = 0;

    foreach ($this->getItems() as $item) {
        $totalBudgetPrice += $item->getPrice();
    }

    return $totalBudgetPrice;
}

/**
 * @return decimal
 */
public function calculateInstallmentRatePrice()
{
    return $this->calculateTotalBudgetPrice() / $this->getInstallmentRate();
}

/**
 * @ORM\PrePersist
 * @ORM\PreUpdate
 */
public function onPreEvents()
{
    $this->setNextPaymentDate($this->generateNextPaymentDate());
    $this->setInstallmentRatePrice($this->calculateInstallmentRatePrice());
    $this->setTotalBudgetPrice($this->calculateTotalBudgetPrice());
}

The method generateNextPaymentDate() is normally executed and uses the field value starts_at, a field of sorts DateTime, of the entity Budget. Inserting a new one or updating an existing one, the method works normally, having its value returned inserted/updated in the bank.

Already the methods calculateInstallmentRatePrice() and calculateTotalBudgetPrice() use the field value meters, a whole type field of the entity Product, which is a Collection form embedded in the form Budget. The methods work, but it is necessary that I have changed some field of the main form, any other value, for these methods to have their values persisted in the bank. Otherwise, they are normally executed but are not updated.

I don’t know how to fix it. I must have forgotten something?