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Date: Wed, 28 Oct 2015 14:40:57 +0000
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Subject: Re: [PHP-DEV] In a destructor, how to detect if an exception is
 currently in flight?
From: rowan.collins@gmail.com (Rowan Collins)

Erik van Velzen wrote on 28/10/2015 13:28:
>      try {
>          $scope = new ScopeGuard;
>
>          $scope->onSucces(function() { logTransactionOne(); });
>          $scope->onFailure(function() { rollbackTransationOne(); });
>          doTransactionOne();
>
>          $scope->onSuccess(function() { logTransactionTwo(); });
>          $scope->onFailure(function() { rollbackTransactionTwo(); });
>          $scope->onExit(function() { cleanupTransactionTwo(); });
>          doTransactionTwo();
>      }
>      catch (\Throwable $e) {
>          $scope->callFailureHandlers();
>          throw $e;
>      }
>      finally {
>          $scope->callExitHandlers();
>      }
>
>      $scope->callSuccessHandlers();

Did you see Johannes' suggestion re explicit success vs implicit failure?

$scope = new ScopeGuard;

$scope->onSucces(function() { logTransactionOne(); });
$scope->onFailure(function() { rollbackTransationOne(); });
doTransactionOne();

$scope->onSuccess(function() { logTransactionTwo(); });
$scope->onFailure(function() { rollbackTransactionTwo(); });
$scope->onExit(function() { cleanupTransactionTwo(); });
doTransactionTwo();

$scope->registerSuccess();


The ScopeGuard's destructor can now detect the condition:

if ( $this->success_registered ) {
    // Function reached checkpoint for this scope
    $this->callSuccessHandlers();
} else {
    // Function aborted early, due to a throw or early return
    $this->callExitHandlers();
}
$this->callExitHandlers();


No boilerplate throw-catch needed, works even if there is already a catch or finally within the function's definition.

In fact, I kind of want to use this somewhere now... ;)

Regards,
-- 
Rowan Collins
[IMSoP]