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Date: Wed, 30 Apr 2008 01:14:21 +0100
Reply-To: RQuadling@GoogleMail.com
To: "Robert Cummings" <robert@interjinn.com>
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Subject: Re: [PHP-DEV] Class Properties in Interfaces?
From: rquadling@googlemail.com ("Richard Quadling")

2008/4/30 Robert Cummings <robert@interjinn.com>:
>
>  On Tue, 2008-04-29 at 20:04 +0200, John Carter -X (johncart - PolicyApp
>
> Ltd at Cisco) wrote:
>  > I think there's been two responses to this query:
>  >
>  > 1. We can't have properties in interfaces because interfaces don't have
>  > properties. I would say this is tautological and doesn't add anything.
>  >
>  > 2. Why would you need to? Getters and setters work.
>  >
>  > So I suppose to answer my question for myself, there's no real technical
>  > reason for not having properties in interfaces, but getters and setters
>  > work just fine and no-one (including me) really misses them.
>
>  I have to agree. Enforcing existence of a property is just as much part
>  of an interface as enforcing the existence of a method. Why go down the
>  clutzy getter and setter method route when properties were meant to be
>  accessed. Why should code be made slower? Methods are at least an order
>  of magnitude slower than direct property access.
>
>  Cheers,
>  Rob.
>  --
>  http://www.interjinn.com
>  Application and Templating Framework for PHP

There are some advantages.

1 - Read only / write only properties can be created more obviously,
rather than having the logic spread thoughout the __magic_functions.
2 - Automatic document tools get a real benefit from having a defined
mechanism to work from.

Using a simple shape class, it is a toss up between $shape->getArea()
vs $shape->area

If PHP supported setters/getters in this way, then the interface for a
shape would have a fCalcArea member function requirement. You may want
to have the area updated upon the change of any of the dimensions.

Ideally the interface should also have a read only property of area,
but the support of properties in an interface is disputed here. In
this limited example, it would seem useful.

Richard.

-- 
-----
Richard Quadling
Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&r=213474731
"Standing on the shoulders of some very clever giants!"