Hello Stephane,
you're right $that must be available in the derived __clone().
Thursday, January 22, 2004, 3:37:11 PM, you wrote:
> I'm currently using PHP4 and I'm evaluating PHP5 for its new exciting features.
> I have some remarks, split into distinct posts.
> The first one is about the current implementation of __clone():
> * a derived __clone() can't call parent::__clone() because $that is
> only declared for the first __clone() call. So a derived __clone() has to
> include the code of its parent's __clone(). It's not only bad programming,
> but it can't work when a parent implements private members.
> * when a class implements __clone(), all its derived classes have also
> to implement it to transfer their own members.
> There are a several possibilities to get round the first point, but in
> order to also simplify __clone() implementation, here is a way it could be
> implemented, close to __construct() implementation:
> * the system firstly does a bit for bit copy of the source object,
> * then it calls __clone() (which at worst does nothing, if no class implements it),
> * __clone() accesses members using $this to handle those (and only
> those) that need particular actions,
> * this is the responsibility of a derived __clone() to call (or not)
> parent::__clone().
> Advantages:
> * same behaviour as __construct(), except that $this is already initialized,
> * it guaranties that all members will be transfered, by reference for objects, by
> copy for the others,
> * __clone() just needs to be implemented to handle members that need particular
> actions,
> * derived classes do not need to implement __clone() when one of its parents does,
> * no more need of $that.
> In terms of performance, I don't think this implementation is bad,
> because a bit for bit copy is certainly faster than an interpreted
> member-to-member transfer, except if all members have to be handled in a
> particular way.
> I also consider the __clone() implementation not coherent with its calling syntax.
> Indeed "$newObj = $obj->__clone();" lets think of an implementation like this:
> <?
> class Foo {
> function __clone() {
> $o = new Foo($this->..., $this->...);
> $o->...; // eventually
> return $o;
> }
> }
?>>
> Because __clone() is considered as a copy constructor, it could be
> implemented in a similar way as for object construction, for example:
> "$newObj = clone $obj;", "clone" being a language keyword.
> Regards,
> Stephane
--
Best regards,
Marcus mailto:[EMAIL PROTECTED]
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