Edit report at http://bugs.php.net/bug.php?id=52583&edit=1
ID: 52583
Comment by: rayro at gmx dot de
Reported by: martin dot leucht at gmail dot com
Summary: Improved casting and hinting, new magic method
__cast()
Status: Open
Type: Feature/Change Request
Package: Class/Object related
Operating System: Irrelevant
PHP Version: Irrelevant
Block user comment: N
New Comment:
pretty nice, awesome feature!
but i have some recommendations on this:
1) is it true that i cannot cast to a boolean false? what about throwing
the error if no return was made? the user is able to throw some
exception or will simple not return anything to use the default error
mechanism...
2) i think there should be 2 additional types of functions covering your
2 solutions by simply change the name. for your case 1 this should be
__cast, whereas 2 could be __hint? the essential difference is that
__hint will be called in the functions arguments and __cast will be
called elsewhere?
Previous Comments:
------------------------------------------------------------------------
[2010-10-03 18:45:29] + at ni-po dot com
@degeberg: Doesn't the RFC cover casting the other way round? I.e. Class
-> Scalar
------------------------------------------------------------------------
[2010-08-11 16:54:01] degeb...@php.net
See: http://wiki.php.net/rfc/class_casting_to_scalar
------------------------------------------------------------------------
[2010-08-11 16:30:02] martin dot leucht at gmail dot com
Description:
------------
Type casting in PHP is currently limited to the builtin types. It would
be very useful (IMO) if one could cast a value/variable to a class. And
also type hinting could be improved by casting instead of type checking
only.
I suggest to solve this by introducing a new magic method for classes,
called "__cast()", that accepts the value to cast as parameter.
I see two possible solutions for its functionality:
(1) __cast() replaces the constructor method
This will force the developer to move logics from the constructor into a
separate function/method (which isn't even so bad) or to copy his code
(which is indeed bad). If the function returns with the boolean value
"false", the default error mechanism is started saying something like
"cast to XYZ not allowed".
(2) __cast() acts like a static constructor
The code must return the casted result itself. That means one would
implement some logics to transform the given value to the needed
constructor parameters and create a new instance on his own. To handle
an unsupported value the method would throw an exception or an error.
The negative (or let's say curious) thing about this solution is, that
this cast method could also return a value of a totally different type
(see example).
Test script:
---------------
// see patch file
Expected result:
----------------
// working cast
Actual result:
--------------
// parse errors
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=52583&edit=1
