Edit report at https://bugs.php.net/bug.php?id=61147&edit=1
ID: 61147
Comment by: greywire at gmail dot com
Reported by: greywire at gmail dot com
Summary: No conflict resolution for properties in traits
Status: Suspended
Type: Feature/Change Request
Package: Class/Object related
Operating System: MacOS X 10.7
PHP Version: 5.4.0RC8
Block user comment: N
Private report: N
New Comment:
I'm trying to understand here. When you say alias, do you mean generically
like "reference" or "pointer" to a method? Or is there some aliasing construct
I'm not aware of in the language?
Traits are supposed to be flattened in the class, so its more like a language
assisted cut and paste, correct? Which means two conflicting method names have
to be renamed uniquely (or not named at all?) and then a
reference/alias/pointer to the desired one is put in place with the original
name. I don't know how the traits are actually implemented internally...
Attempting to do this by hand I see that you could, using runkit, remove the
two conflicting methods and put in one "aliased" method pointing to one that
was removed. But doing this with a property as you said results in a new
property that does not affect the other two. I thought maybe you could set
that new property with a "&$obj->renamedprop" but that doesnt work.
Running through my options (thinking about if runkit could be used to fix it.
I've used runkit before to sorta implement my own traits functionality) I see
its a tricky problem to solve indeed.
The only thing I came up with is that if at runtime PHP just removed the
conflicting properties altogether so the code compiles and runs, and then the
two properties (and the needed alias) could just be caught with __get/__set and
handled by the user. You'd get no warning or error about the conflict, but,
you would immediately know about it when you accessed one of the properties.
This may seem like a hack but at least it would give people an option...
Is that a palatable compromise that wouldn't be hard to implement? :)
Previous Comments:
------------------------------------------------------------------------
[2012-02-21 09:26:36] g...@php.net
Unfortunately, the solution is not easy at all.
One reason is the dynamic nature of PHP. You can easily access properties based
on their string name:
$foo = 'bar';
$this->$foo = 'foobar';
For exactly the same reason, we do NOT provide 'renaming'. The conflict
resolution for methods allows to introduce an alias.
Nothing more. An alias is a new name pointing to an unchanged method-body.
(If you think about what that means, note that it breaks recursion in typical
cases.)
Thus, your proposal does not work with the current semantics. It would only
result in a new property in the class that is never actually used.
So far, we refrained from adding any of the constructs proposed in literature,
since they would add considerable complexity.
>From time to time there have been proposals for related features that could
>make
it into a future version of PHP, but for the moment being, I do not see how we
can make this work without changing the nature of PHP.
Suggestions are welcome of course.
Thanks
Stefan
------------------------------------------------------------------------
[2012-02-20 18:59:00] greywire at gmail dot com
Description:
------------
There is no way to resolve a conflict in two used traits with the same
property. The resolution method used to resolve conflicting method names
should be able to be used similarly on properties.
I realize this may be the intended behavior to discourage use of properties in
traits as properties were not originally intended in traits, but since
properties are allowed, there should be a way to resolve the conflict, and the
solution is simple and fits with existing syntax.
Test script:
---------------
<?php
trait testone {
public $test;
}
trait testtwo {
public $test;
}
//** this should work but doesn't
class traittest {
use testtwo, testone {
testone::$test insteadof testtwo;
testtwo::$test as $testalso;
}
}
?>
Expected result:
----------------
No errors or warnings.
Actual result:
--------------
Parse error: syntax error, unexpected '$test' (T_VARIABLE), expecting
identifier (T_STRING) in index.php on line 14
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=61147&edit=1
