Class::Std problem

Herkum has asked for the wisdom of the Perl Monks concerning the following question:

I was running my code and came across this error which was really bizarre.

Can't call method "isa" on an undefined value at /usr/local/share/perl
+/5.8.8/Class/Std.pm line 225.
[download]

The problematic code is,

# This is the values that blow it up
#   @hierarchy = qw(EEBL::League::Schedule);
#   @hierarchy = qw(EEBL::Team EEBL EEBL::Config);

    return @{$_hierarchy_of{$class}}
        = sort { $a->isa($b) ? -1
               : $b->isa($a) ? +1
               :                0
               } @hierarchy;
[download]

Does anyone have any ideas on how i can work around this?

Update: My actual solution for this ended up being using another version of Perl on this box (5.10). I don't think the source of my problem was the code but something in the interpreter(5.8.8 on Linux ubuntu 2.6.18.8).

Comment on Class::Std problem Select or Download Code

Replies are listed 'Best First'.
Re: Class::Std problem by ikegami (Patriarch) on Jan 19, 2009 at 04:56 UTC
That can't be. If `@hierarchy` only contained one element as you claim it does in the first data set, the compare block would never get called. `@hierarchy` actually contains more than one element, one of which is undefined. To see the contents of `@hierarchy`, you can use `use Data::Dumper; print Dumper \@hierarchy;` [download]	[reply] [d/l] [select]
Re^2: Class::Std problem by Herkum (Parson) on Jan 19, 2009 at 05:36 UTC
I used Data::Dumper to print out @hierarchy. That was how I got the array sample data in the original post. Since I have not debugged Class::Std before I was not sure if this was correct behavior or not. Since you are implying it is not, I guess that part needs further looking in to. The other thing was I also included code that returned `@{$hierarchy_of{$class}} = @hierarchy` When it was only a one element array. I still got the same error, which was why I listed two arrays as part of the problem.	[reply] [d/l]
Re^3: Class::Std problem by ikegami (Patriarch) on Jan 19, 2009 at 06:37 UTC
Sorry, but something you said isn't true. `>perl -we"@hierarchy = qw(EEBL::League::Schedule); () = sort { $a->isa +($b) ? -1 : $b->isa($a) ? +1 : 0 } @hierarchy;" >perl -we"@hierarchy = qw(EEBL::Team EEBL EEBL::Config); () = sort { $ +a->isa($b) ? -1 : $b->isa($a) ? +1 : 0 } @hierarchy;" >` [download] According to you, code that isn't even executed is issuing a run-time warning. `>perl -we"() = sort { die } 1" >perl -we"() = sort { die } 1,2" Died at -e line 1. >` [download] Find what and you found your problem. The most likely by far is that the content of `@hierarchy` isn't what you think it is. I used Data::Dumper to print out @hierarchy. Please provide the output. Remember to use `Dumper(\@hierarchy)` and not `Dumper(@hierarchy)`. Flattening the array makes the output ambiguous.	[reply] [d/l] [select]
Re^4: Class::Std problem by Herkum (Parson) on Jan 19, 2009 at 14:26 UTC
Re^5: Class::Std problem by ikegami (Patriarch) on Jan 20, 2009 at 04:27 UTC
Re: Class::Std problem by kyle (Abbot) on Jan 19, 2009 at 16:50 UTC
Does one of those classes (EEBL::*) have a `sub isa` that clobbers `$a` or `$b`?	[reply] [d/l] [select]
Re^2: Class::Std problem by Herkum (Parson) on Jan 19, 2009 at 21:04 UTC
I was pretty sure that would be a no, and double-checked. I did not accidentally create my own isa() routine. Something that I had not thought about though.	[reply]

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