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To: Erik van Velzen <erik@evanv.nl>
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Date: Thu, 29 Oct 2015 00:17:54 +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 16:02 +0100, Erik van Velzen wrote:
> I didn't see how it could be generalized but your example clears that up.

Quick attempt of a generalization:

abstract class AbstractRAIIGuard {
    private $succeeded =3D false;

    protected abstract function fail();

    protected function success() {}

    public function succeed() {
        if (!$this->succeeded) {
            throw new RAIIAlreadyMarkedAsSuccessfulException();
        }
        $this->success();
        $this->succeeded =3D true;
    }

    public function __destruct() {
        if (!$this->succeeded) {
            $this->fail();
        }
    }
}

class CallbackRAIIGuard extends AbstractRAIIGuard {
    private $success;
    private $fail;

    public __construct(callable $fail, callable $success =3D null) {
        $this->success =3D $success;
        $this->fail =3D $fail;
    }

    protected function fail() {
        call_user_func($this->fail());
    }

    public function success () {
        if ($this->success) {
            call_user_func_array($this->success, func_get_args());
        }
    }
}

class DBRAII extends AbstractRAII {
    private $db;
    public function __construct(DB $db) {
        $this->db =3D $db;
        $db->begin();
    }

    protected function fail() {
        $this->db->rollback();
    }

    public function success () {
        $this->db->commit();
    }
}

function foo(DB $db) {
    $guard =3D new DBRAII($db);

    // or using the more generic class

    $guard =3D new CallbackRAIIGuard(
        [$db, "rollback"], [$db, "commit"]
    );
   =20
    // ....

    $guard->succeed();
}

johannes

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