private function writeAttribute(WriterHelper $writer, ClassMetadata $classMetadata, $fieldName, $fieldValue)
{
$name = $classMetadata->getFieldXmlName($fieldName);
$type = $classMetadata->getTypeOfField($fieldName);
$mapping = $classMetadata->getFieldMapping($fieldName);
$prefix = isset($mapping['prefix']) ? $mapping['prefix'] : null;
if ($classMetadata->isCollection($fieldName)) {
$convertedValues = array();
foreach ($fieldValue as $value) {
$convertedValues[] = Type::getType($type)->convertToXmlValue($value);
}
$writer->writeAttribute($name, implode(" ", $convertedValues), $prefix);
} else {
$writer->writeAttribute($name, Type::getType($type)->convertToXmlValue($fieldValue), $prefix);
}
}