Clint M Priest | 1 Mar 01:45 2012

RE: [PHP-DEV] [Draft RFC] Object Casting and Assignment Handlers

As much as I would love to have __castTo() and __assign() I have to agree with Stas here that it fundamentally
changes the mechanics of if($object) and unfortunately turns that simple if statement into a possible
hour long hunt to find the code that is doing the damage, if it is even considered a possibility by someone
reading the code.

For the record, I really have only ever needed something like __toArray() so that objects implementing
ArrayAccess could be passed to array internal functions.

I am interested in object natives though, which this is leading in the direction of.

-Clint

-----Original Message-----
From: Stas Malyshev [mailto:smalyshev <at> sugarcrm.com] 
Sent: Wednesday, February 29, 2012 1:48 AM
To: Anthony Ferrara
Cc: internals <at> lists.php.net
Subject: Re: [PHP-DEV] [Draft RFC] Object Casting and Assignment Handlers

Hi!

> Hey all,
>
> I've created a draft version of the RFC for implementing __castTo() 
> and __assign():
>
> https://wiki.php.net/rfc/object_cast_magic

I think having cast method may have merits, though use cases where objects need to be converted to scalars
that aren't string are very limited, and cases where they need to do so transparently are almost
non-existent. I think what outlined in the RFC is a backdoor operator overloading, through rather
complex and unobvious magic. My opinion is that outside of very limited number of cases (such as
implementing complex numbers or matrix algebra - and how frequently would one need do that in PHP anyway?)
operator overloading is way more trouble than it's worth and makes code nearly unreadable as you never
know what exactly each operator does. For example, if($object) would have completely different
semantics than before, for some objects but not other, and without any obvious clue to the user what it
actually does - and all that to save couple of keystrokes on if($object->valid())?

Still, if there's a valid use case found, cast magic method and "unboxing" method may have merit. So far the
cases outlined seem either too artificial and narrow for language-level functionality, or plain wrong
(like SplFixedArray example - nothing in this proposal would enable it to work with sort, for example).
But I do not exclude other cases can exist.

However, assignment overloading does not seem viable to me.
Also, I'm not sure how this is possible technically: $obj = {expression} is supposed to replace $obj with
the result of the expression, not call methods on $obj. Doing otherwise would be huge change in the
semantics, a complete no go. Also, it's impossible if $obj is not set - meaning, code $obj = 1 would mean
totally different things depending on if $obj is set or not - again, not a good idea. It also does not cover
many corner cases but I don't even want to go there since an idea to change semantics of the assignment seems
very wrong to me in principle, so no need to go into the fine details.
--
Stanislav Malyshev, Software Architect
SugarCRM: http://www.sugarcrm.com/
(408)454-6900 ext. 227

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Gmane