php-developer-list | 2002112

Re: [PHP-DEV] ZE2 + public/protected/private/final From: Marcus Börger (marcus.boerger <email protected>)
Date: 11/29/02

At 17:40 29.11.2002, Andi Gutmans wrote:
>At 06:25 PM 11/28/2002 +0100, Marcus Börger wrote:
>>With current ZE2 it is possible to instanciate an abstract class. That is
>>a class
>>that has at least one abstract method. When we add a flag field to
>>class_entry
>>struct we can handle this. We simply need to set an abstract flag for the
>>class
>>entry when any abstract method is added or inherited.
>>
>>I updated the full patch to do it that way:
>>http://marcus-boerger.de/php/ext/ze2/ze2-f3p-21128.diff.txt
>
>I thought about this but am not quite sure how I feel about this. I know
>that theoretically in C++ and Java you can't instantiate such classes but
>I'm not sure it'd be too bad in PHP.
>If I were to implement this I'd probably use a counter to *remember* how
>many abstract methods a class has.
>
>Andi

I would like a list of abstract methods in case the error is at hand more.
On the other side i do not know if the check is what we want. I mean it
keeps you away
from using abstract classes what is a must in C++/Java. But for PHP this is
only valid
as long as we do not:
a) allow to dynamically add new methods to instances/classes
  (This would make some more thinks complicated but makes PHP more object
oriented)
b) explicitly allow using abstract classes by decision here

Also the check has one negative aspect: it cost time (even thogh only a few
small tests).

Your counter would be slower and could instead be simply computed when the
error is
being generated. See pseudo code:
cnt = 0
foreach function in function_table
   if function->common.fn_flags & FN_ABSTRACT
     cnt++

Since there is until now no need to change the class_entry while inheriting
a method we
can also show the class in which the method was introduced. Maybe like
shown below:

class test {
     abstract funcition a();
}
class fail extends test {
}

$t = new fail();
Fatal Error: You cannot instanciate abstract class fail (abstract methods:
test::a)

marcus

p.s. I updated the complete patch:
http://marcus-boerger.de/php/ext/ze2/ze2-f3p-21129.diff
after your commit. 

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