in reply to (tye)Re: ref, no, maybe?
in thread ref, no, maybe?

>By the way, how do you tell if a reference is blessed without using the fragile hack

I've always used variations of: 

        if ($type = ref $t) {
                eval { $t->isa("UNIVERSAL"); };
                if ( $@=~/unblessed/ ) {
                        print "It's a $type, not blessed.\n"
                } else {
                        print "It's blessed into class $type";
                }
        } else {
                print "Not a reference at all\n";
        }

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with great success. It may not catch everything, and normally I'm not hunting around to figure out what's in a variable... If you don't know, you're in bigger trouble than this. :)

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can in Re: ref, no, maybe?
by jeroenes (Priest) on Jan 11, 2001 at 14:04 UTC
    This thread strongly reminds me of Readonly error on $_. In his response, merlyn displays some trick using the can method. /me thinks it can be applied here also. Saves the use of UNIVERSAL, but uses eval. 
    if eval( $r->can('can')) {
    #we have an object
} elsif ref( $r) {
    #we have an unblessed reference
} else {
    #no reference at all
}

    [download]
    Merlyn's solution looks somewhat cleaner to me. What do you think?

    Jeroen
    I was dreaming of guitarnotes that would irritate an executive kind of guy (FZ)

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[d/l]

      I'd rewrite your code like this: 

      if(  ! ref($r)  ) {
    #no reference at all
} elsif(  ! eval { $r->can('can') }  ) {
    #unblessed ref
} else {
    #blessed ref
}

      [download]
      because I think the eval{} seems likely to be more expensive than the ref(). But even more important, if $r is, for example, the simple string "My::Package", then $r->can('can') will succeed (which is also a bug in merlyn's version), even if there is no package called My::Package. In fact, try "This is a test"->can('can') for fun. (:

      As for the difference between eval { $r->can('can') } and eval { $r->isa('UNIVERSAL') }, the only advantage I see to the first is fewer keystrokes. I find the latter clearer, personally. But that gave me the idea for $r->can('isa'), which I find clear (as well as short). I guess isa() screams "object" to my brain faster than can() does, not sure why.

              - tye (but my friends call me "Tye")
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[d/l]
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(tye)Re2: ref, no, maybe?
by tye (Sage) on Jan 11, 2001 at 05:45 UTC

    Ah, thanks. I was wanting to use it to avoid the eval, so I guess I'll just keep the eval. (:

            - tye (but my friends call me "Tye")
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