Type converters

Type converters are commonly used when it is necessary to convert from one type into another. They are usually applied in the Extbase controller in the initialize<actionName>Action() method.

For example a date might be given as string in some language, "October 7th, 2022" or as UNIX time stamp: 1665159559. Your action method, however, expects a \DateTime object. Extbase tries to match the data coming from the frontend automatically.

When matching the data formats is expected to fail you can use one of the type converters provided by Extbase or implement a type converter yourself by implementing the interface \TYPO3\CMS\Extbase\Property\TypeConverterInterface .

You can find the type converters provided by Extbase in the directory EXT:extbase/Classes/Property/TypeConverter.

Custom type converters

A custom type converter must implement the interface \TYPO3\CMS\Extbase\Property\TypeConverterInterface . In most use cases it will extend the abstract class \TYPO3\CMS\Extbase\Property\TypeConverter\AbstractTypeConverter , which already implements this interface.

All type converters should have no internal state, such that they can be used as singletons and multiple times in succession.

The registration and configuration of a type converter is done in the extension's ext_localconf.php:

EXT:my_extension/ext_localconf.php 
<?php

declare(strict_types=1);

use MyVendor\MyExtension\TypeConverter\MyDatetimeConverter;
use TYPO3\CMS\Extbase\Utility\ExtensionUtility;

defined('TYPO3') or die();

// Starting  with TYPO3 v12 extbase type converters are registered in
// Configuration/Services.yaml
if ((new \TYPO3\CMS\Core\Information\Typo3Version())->getMajorVersion() < 12)
{
    // Register type converters
    ExtensionUtility::registerTypeConverter(MyDatetimeConverter::class);
}
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