Calling a chain of services¶
It is also possible to use services in a “chain”. This means using all the available services of a type instead of just one.
The method \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstanceService()
accepts a third
parameter to exclude a number of services, using a comma-separated
list of service keys. This way you can walk through all available
services of a type by passing the already used service keys. Services
will be called in order of decreasing priority and quality.
The following example is an extract of the user authentication process:
// Use 'auth' service to find the user
// First found user will be used
$serviceChain = '';
$subType = 'getUser' . $this->loginType;
while (is_object($serviceObj = GeneralUtility::makeInstanceService('auth', $subType, $serviceChain))) {
$serviceChain .= ',' . $serviceObj->getServiceKey();
$serviceObj->initAuth($subType, $loginData, $authInfo, $this);
if ($row = $serviceObj->getUser()) {
...
// User found, just stop to search for more if not configured to go on
if (!$this->svConfig['setup'][$this->loginType . '_fetchAllUsers']) {
break;
}
}
}
As you see the while loop is exited when a service gives a result. More sophisticated mechanisms can be imagined. In this next example – also taken from the authentication process – the loop is exited only when a certain value is returned by the method called:
// Use 'auth' service to authenticate the user
// If one service returns FALSE then authentication failed
// a service might return 100 which means there's no reason to stop but the user can't be authenticated by that service
while (is_object($serviceObj = GeneralUtility::makeInstanceService('auth', $subType, $serviceChain))) {
$serviceChain .= ',' . $serviceObj->getServiceKey();
$serviceObj->initAuth($subType, $loginData, $authInfo, $this);
if (($ret = $serviceObj->authUser($tempuser)) > 0) {
// If the service returns >=200 then no more checking is needed - useful for IP checking without password
if ((int)$ret >= 200) {
$authenticated = true;
break;
} elseif ((int)$ret >= 100) {
} else {
$authenticated = true;
}
} else {
$authenticated = false;
break;
}
}
In the above example the loop will walk through all services of the
given type except if one service returns false
or a value larger than
or equals to 200, in which case the chain is interrupted.