gistfile1.php

    /**
     * This method can be overwritten to tweak to form construction, by default the form
     * is built by reading the FieldDescription
     *
     * @return void
     */
    protected function configureFormFields(Form $form)
    {

        foreach ($this->getFormFields() as $fieldDescription) {

            if (!$fieldDescription->getType()) {

                continue;
            }

            $this->addFormField($form, $fieldDescription);
        }

    }

    protected function addFormField($form, $name, array $options = array())
    {

        $field = false;
        
        $object = $form->getData();

        if ($name instanceof FieldDescription) {

            $fieldDescription = $name;
            $name = $fieldDescription->getName();

        } else if ($name instanceof FormInterface) {

            $field   = $name;
            $name    = $field->getKey();
            
            $fieldDescription = new FieldDescription;
            $fieldDescription->setFieldName($name);

            $this->fixFormFieldDescription($fieldDescription);
            $this->formFields[$name] = $fieldDescription;

        } else if (is_string($name) && !array_key_exists($name, $this->formFields)) {
            // the provided $name

            $fieldDescription = new FieldDescription;
            $fieldDescription->setFieldName($name);

            $this->fixFormFieldDescription($fieldDescription);
            $this->formFields[$name] = $fieldDescription;
        } else if (is_string($name) && array_key_exists($name, $this->formFields)) {
            $fieldDescription = $this->formFields[$name];
        }

        if(!$field) {
            switch ($fieldDescription->getType()) {

                case ClassMetadataInfo::ONE_TO_MANY:

                    $field = $this->getOneToManyField($object, $fieldDescription);
                    break;

                case ClassMetadataInfo::MANY_TO_MANY:

                    $field = $this->getManyToManyField($object, $fieldDescription);
                    break;

                case ClassMetadataInfo::MANY_TO_ONE:
                    $field = $this->getManyToOneField($object, $fieldDescription);
                    break;

                case ClassMetadataInfo::ONE_TO_ONE:
                    $field = $this->getOneToOneField($object, $fieldDescription);
                    break;

                default:
                    $class   = $this->getFormFieldClass($fieldDescription);
                    $options = $fieldDescription->getOption('form_field_options', array());

                    // there is no way to use a custom widget with the FieldFactory
                    if($class) {
                        $field = new $class($fieldDescription->getFieldName(), $options);
                    } else {
                        $field = $this->container->get('form.field_factory')->getInstance($this->getClass(), $fieldDescription->getFieldName(), $options);
                    }
            }
        }
        
        $form->add($field);
    }

    /**
     * return a form depend on the given $object and FieldDescription $fields array
     *
     * @throws RuntimeException
     * @param  $object
     * @return Symfony\Component\Form\Form
     */
    public function getForm($object)
    {

        $form = $this->getBaseForm($object);

        $this->configureFormFields($form);
        
        return $form;
    }