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Subject: Re: [PHP-DEV] horizontal reuse: traits vs. grafts
From: mathieu.suen@easyflirt.com ("mathieu.suen")

Stefan Marr wrote:
> On 25 Mar 2010, at 21:30, Stefan Marr wrote:
>   
>> On 25 Mar 2010, at 16:37, Lukas Kahwe Smith wrote:
>>     
>>> Hi,
>>>
>>> this was just brought up on IRC. my understanding is that traits have no concept of properties, but grafts do (all hidden internally). correct?
>>>       
>> Right, the Traits proposal as it is at the moment, avoids the explicit discussion of state.
>> This is not a restriction per se, but could limit the composability of traits.
>>
>> To ensure composibility, you would have to resort to abstract methods which are implemented by the composing class.
>>     
> Maybe I should clarify that.
>
> Currently the semantics is implicitly the following:
>
> class Base{
>  var $a;
> }
>
> trait T1 {
>  var $a;
>  var $b;
> }
>
> trait T2 {
>  var $a;
>  var $c;
> }
>
> class Composite extends Base {
>  use T1, T2;
> }
>
> and Composite would have the instance variables $a, $b, $c.
> The problem would be of course that Base, T1, and T2 could use $a for completely different things.
>
> Simple, but at the cost of composability/safety.
> But for most practical cases that should be 'good enough'. As already mentioned, if you want stronger guarantees, state accessor methods can be used.
>
> However, I think this implication is not discussed in the RFC, and works just because PHP can create the fields dynamically. Thus, I used 'var' here in the example, instead of defining a semantics and handling for public, private, protected.
>
> Best regards
> Stefan
Variable has been discuss in *http://tinyurl.com/y9t7nd9

--Mathieu Suen
*