What's a better way to validate an array ref than "if( 'ARRAY' eq ref $foo )"? Thanks!

There are caveats whichever way you do it, but currently I tend to default to just derefing it within an eval block:

if (eval{ use strict 'refs'; @$foo; 1 }) {
  # it is, or pretends convincingly, to be an array ref
}
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Caveat? Right. In the presence of ties or overloading, there may be side effects to derefing it. Pick your poison / buyer beware / etc.

The problem I have with isa() is that I either need to use the verbose UNIVERSAL::isa( $foo, 'Object::Foo' ) syntax, or check the return of ref() to be sure that I can do $foo->isa('Object::Foo') without dying.

Wrapping every isa() check in an eval{} seems cumbersome, too.

After a bit of poking, Scalar::Util's  blessed() and reftype() look like pretty good options. I suppose I could just import isa(), as well.

Beware.

The problem I have with isa() is that I either need to use the verbose UNIVERSAL::isa( $foo, 'Object::Foo' ) syntax...

Unfortunately, it's completely wrong. See Acme::UNIVERSAL::new if you think it's a good idea.

Wrapping every isa() check in an eval{} seems cumbersome, too.

Tough. If you care about getting the right answer, that's what you need to do. Yes, the syntax is a little clunky, but it will give you the right answer. Nothing else will.

I suppose I could just import isa(), as well.

Not if you care about getting the right answer.

There's some real food for thought in your replies, thanks.

So if get the point, there is no easy way to test whether something can be treated as a hash ref (for instance) short of trying to do so. So the best way to test is to try and catch any exceptions that indicate failure.

If I want to verify membership in a class, I'd need to do something like:

# Option 1.
if ( eval { $foo->isa('Some::Class') } ) {
  
  # Do stuff with Some::Class
}

# or Option 2.

use Scalar::Util;

if ( blessed $foo and $foo->isa('Some::Class') ) {
  # Do stuff with Some::Class
}
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Are there any big ugly problems with either option? I've tested both and they seem OK, but there's no point trying to learn a new habbit, if it's a bad one!


TGI says moo