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To: Erik van Velzen <erik@evanv.nl>
Cc: internals@lists.php.net
Date: Wed, 28 Oct 2015 12:13:34 +0100
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Subject: Re: [PHP-DEV] In a destructor, how to detect if an exception is
 currently in flight?
From: johannes@schlueters.de (Johannes =?ISO-8859-1?Q?Schl=FCter?=)

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On Wed, 2015-10-28 at 11:00 +0100, Erik van Velzen wrote:
> Subject says it all.
>=20
> I want to make a small "ScopeGuard" library for exception-safe
> transactions, like the following:
>=20
>     $scope =3D new ScopeGuard;
>=20
>     $scope->onSucces(function() { logTransactionOne(); });
>     $scope->onFailure(function() { rollbackTransationOne(); });
>     doTransactionOne();
>=20
>     $scope->onSuccess(function() { logTransactionTwo(); });
>     $scope->onFailure(function() { rollbackTransactionTwo(); });
>     $scope->onFailure(function() { logFailureOfTransactionTwo(); });
>     doTransactionTwo();
>=20
>     // ... Three Four etc...
>=20
> So if an exception is thrown the attached onFailure callbacks will be
> executed, if the scope is exited through a return however the success
> callbacks will be executed.

The way to do this is by marking the success in an explicit way. See
http://slides.com/johannes4321/froscon15/#/4 and
http://slides.com/johannes4321/froscon15/#/6

With your attempt you can only handle abortion via exception. With a
pattern like shown in my slides you can also handle cases where you
"return" early nicely.

johannes


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