Populates a SilverStripe Form subclass with DataObject values

PopulateFormDefaults.php

<?php

class MyForm extends Form 
{    
    /**
     * @param Customer $customer
     * @return $this
     */
    public function setObject(DataObject $object)
    {
        $fields = self::Fields();

        /** @var FormField $field */
        foreach ($fields as $field) {
            $value = $field->getName();

            if ($object->{$value}) {
                $field->setValue($object->{$value});
            }
        }

        return $this;
    }
}