On 6/16/05, Mark Jason Dominus <[EMAIL PROTECTED]> wrote:
> yves:
> > Using UNIVERSAL::isa() is IMO bad as its suseptible to
> >
> > my $obj=3Dbless [],'HASH';
> >
> > type nonsense.
>
> Perhaps, but it seems to me that someone doing that is doing it
> deliberately to try to deceive the UNIVERSAL::isa function. In which
> case it is a feature, not a bug.
Well, IMO reftype() is superior as its faster and cant be fooled. But
only insofar as the question being asked is "Is the underlying
reference to a legitimate hash".
But the other point, about overload is also important. If an object of
class Foo::Bar overloads hash dereferencing then it too probably
should be consider to be isa('HASH') but it isnt.
So theres three possible questions:
1. Is the object underneath the hood implemented with a given perl type
2. Is the object a member of the class TYPE or a class that inherits from it
3. Does the object provide an TYPE like interface.
The first one can only be reliably done with reftype. the second with
isa, the third with reftype and overload.
All im trying to say here is that the subject is not so simple as to
admit that "isa is the recommended way to do this". IMO in fact isa is
NOT the recommended way to do this.
Although that still begs the question what "this" is. In the code that
chromatic removed IMO the question being asked is 3 which isnt
answered properly by isa() because it ignores classes that arenot
isa('HASH') but do overload hash dereferencing, and conversly can be
fooled by objects that are isa('HASH') but arent reftype() eq 'HASH'
and arent overloaded.
yves
--
perl -Mre=debug -e "/just|another|perl|hacker/"
