Re: Re: Re: OO Perl: calling a constructor within a class

In general using this code can cause an error, unless you can be sure that if $me is a reference that it is a blessed reference.

It is this that led to people doing

if(ref($me) && UNIVERSAL::isa($me,'my_class_name')) {

which is ugly, IMO.

The Scalar::Util package, that as of 5.7.2 is part of the perl distribution, contains a sub blessed() to get around this

if(blessed($me) && $me->isa('my_class_name')) {

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Re: Re: Re: Re: OO Perl: calling a constructor within a class by runrig (Abbot) on Sep 26, 2001 at 22:35 UTC
`if(ref($me) && UNIVERSAL::isa($me,'my_class_name')) {` [download] If you're doing a functional call, then there's no reason for the '`ref($me) &&`' in that expression, though I think you get a warning on earlier versions of perl (not sure how early) if '`$me`' is undefined, so you might say: `if(defined($me) && UNIVERSAL::isa($me,'my_class_name')) {` [download] Then again, you could just leave out the first part and turn off warnings locally :-) Update: Correction by tye duly noted. If I could transfer all the votes/XP from this node to yours I would...(maybe it could be a feature that our overworked fearless leader could implement someday :)	[reply] [d/l] [select]
Re: Re: Re: Re: Re: OO Perl: calling a constructor within a class by tye (Sage) on Sep 27, 2001 at 21:32 UTC
No, you need the `ref($me)` to ensure that $me isn't just some string because UNIVERSAL::isa would then try to use that string as a package name to see if the named package inherits from your class. So to check whether $me is an object, you have to do both. - tye (but my friends call me "Tye")	[reply] [d/l]