# Implementing a Service¶

There are no tools to get you started coding a new service. However there is not much that needs to be done.

A service should be packaged into an extension. This means that you will need at least a declaration file ext_emconf.php and an extension’s icon. The class file for your service should be located in the Classes/Service directory.

Finally the service registration is placed in the extension’s ext_localconf.php file.

## Service Registration¶

Registering a service is done inside the ext_localconf.php file. Let’s look at what is inside.

<?php
if (!defined ('TYPO3_MODE')) {
}

// Extension Key
'babelfish',
// Service type
'translator',
// Service key
'tx_babelfish_translator',
array(
'title' => 'Babelfish',
'description' => 'Guess alien languages by using a babelfish',

'subtype' => '',

'available' => true,
'priority' => 60,
'quality' => 80,

'os' => '',
'exec' => '',

'className' => \Foo\Babelfish\Service\Translator::class
)
);


A service is registered with TYPO3 CMS by calling \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addService(). This method takes the following parameters:

$extKey (string) The key of the extension containing the service.$serviceType
(string) Service type of the service. Choose something explicit.
$serviceKey (string) Unique key for the service. Choose something explicit.$info

title
(string) The title of the service.
description

(string) The description. If it makes sense it should contain information about

• the quality of the service (if it’s better or not than normal)
• the OS dependency (either WIN or UNIX)
• the dependency on external programs (perl, pdftotext, etc.)
subtype

(string / comma-separated list) The subtype is not predefined. Its usage is defined by the API of the service type.

Example:

'subtype' => 'jpg,tif'

available

(boolean) Defines if the service is available or not. This means that the service will be ignored if available is set to false.

It makes no sense to set this to false, but it can be used to make a quick check if the service works on the system it is installed on:

Examples:

// Is the curl extension available?
'available' => function_exists('curl_exec'),


Only quick checks are appropriate here. More extensive checks should be performed when the service is requested and the service class is initialized.

Defaults to true.

priority

(integer) The priority of the service. A service of higher priority will be selected first. Can be reconfigured.

Use a value from 0 to 100. Higher values are reserved for reconfiguration in local configuration. The default value is 50 which means that the service is well implemented and gives normal (good) results.

Imagine that you have two solutions, a pure PHP one and another that depends on an external program. The PHP solution should have a priority of 50 and the other solution a lower one. PHP-only solutions should have a higher priority since they are more convenient in terms of server setup. But if the external solution gives better results you should set both to 50 and set the quality value to a higher value.

quality

(integer/float) Among services with the same priority, the service with the highest quality but the same priority will be preferred.

The use of the quality range is defined by the service type. Integer or floats can be used. The default range is 0-100 and the default value for a normal (good) quality service is 50.

The value of the quality should represent the capacities of the services. Consider a service type that implements the detection of a language used in a text. Let’s say that one service can detect 67 languages and another one only 25. These values could be used directly as quality values.

os

(string) Defines which operating system is needed to run this service.

Examples:

// runs only on UNIX
'os' => 'UNIX',

// runs only on Windows
'os' => 'WIN',

// no special dependency
'os' => '',

exec

(string / comma-separated list) List of external programs which are needed to run the service. Absolute paths are allowed but not recommended, because the programs are searched for automatically by \TYPO3\CMS\Core\Utility\CommandUtility. Leave empty if no external programs are needed.

Examples:

'exec' => 'perl',

'exec' => 'pdftotext',

className

(string) Name of the PHP class implementing the service.

Example:

'className' => \Foo\Babelfish\Service\Translator::class


## PHP Class¶

The PHP class corresponding to the registered service should extend the base service class (\TYPO3\CMS\Core\Service\AbstractService).

It should then implement the methods that you defined for your service’s public API, plus whatever method is relevant from the base TYPO3 CMS service API, which is described in details in the next chapter.