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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 an array 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 user found will be used
$subType = 'getUser' . $this->loginType;
foreach ($this->getAuthServices($subType, $loginData, $authInfo) as $serviceObj) {
if ($row = $serviceObj->getUser()) {
$tempuserArr[] = $row;
$this->logger->debug('User found', [
$this->userid_column => $row[$this->userid_column],
$this->username_column => $row[$this->username_column],
]);
// User found, just stop to search for more if not configured to go on
if (!$this->svConfig['setup'][$this->loginType . '_fetchAllUsers']) {
break;
}
}
}
protected function getAuthServices(string $subType, array $loginData, array $authInfo): \Traversable
{
$serviceChain = '';
while (is_object($serviceObj = GeneralUtility::makeInstanceService('auth', $subType, $serviceChain))) {
$serviceChain .= ',' . $serviceObj->getServiceKey();
$serviceObj->initAuth($subType, $loginData, $authInfo, $this);
yield $serviceObj;
}
if ($serviceChain) {
$this->logger->debug($subType . ' auth services called: ' . $serviceChain);
}
}
As you see the while loop is exited when a service gives a result. More sophisticated mechanisms can be imagined. In this next example – also taken from the authentication process – the loop is exited only when a certain value is returned by the method called:
foreach ($tempuserArr as $tempuser) {
// Use 'auth' service to authenticate the user.
// If one service returns FALSE then authentication fails.
// A service may return 100 which means there's no reason to stop but the
// user can't be authenticated by that service.
$this->logger->debug('Auth user', $tempuser);
$subType = 'authUser' . $this->loginType;
foreach ($this->getAuthServices($subType, $loginData, $authInfo) as $serviceObj) {
if (($ret = $serviceObj->authUser($tempuser)) > 0) {
// If the service returns >=200 then no more checking is needed.
// This is useful for IP checking without password.
if ((int)$ret >= 200) {
$authenticated = true;
break;
}
if ((int)$ret >= 100) {
} else {
$authenticated = true;
}
} else {
$authenticated = false;
break;
}
}
if ($authenticated) {
// Leave foreach() because a user is authenticated
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.