Can't call method on an undefined value?

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

I'm having a really hard time figuring this one out. Every time I compile it says: Can't call method "name" on an undefined value at ./test.pl line 9.

### test.pl ###
use Employee
my $person = Employee->new();
$person->name("bob");
$name = $person->name;
print "hello, ";
print $name;

### Employee.pm ###
package Employee;
use strict;
sub new {
    my $invocant = shift;    
    my $class    = ref($invocant) || $invocant; 
    my $self     = { };
    bless($self, $class);                        
    $self->{name}     = "unknown";    
    return $self;
}
sub name {
    my $self =  shift;
    if (@_) { $self->{name} = shift; }
    return  $self->{name};
}
1;
[download]

Comment on Can't call method on an undefined value? Download Code

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Re: Can't call method on an undefined value? by dragonchild (Archbishop) on Apr 11, 2005 at 14:45 UTC
Try adding strict to test.pl and warnings to both. Your bug will be readily apparent. :-) My wife's blog	[reply]
Re^2: Can't call method on an undefined value? by ysth (Canon) on Apr 11, 2005 at 16:09 UTC
It's a cute little bug, isn't it? I don't actually think it will be necessarily apparent though. With test.pl: `use strict; use warnings; use Employee my $person = Employee->new(); $person->name("bob"); $name = $person->name; print "hello, "; print $name;` [download] I get: `Global symbol "$person" requires explicit package name at test.pl line + 5. Global symbol "$name" requires explicit package name at test.pl line 6 +. Global symbol "$person" requires explicit package name at test.pl line + 6. Global symbol "$name" requires explicit package name at test.pl line 8 +.` [download] It's obvious that $name needs a declaration to make strict happy, but you could still sit and stare at the $person warnings and not realize why it's complaining. The problem is the missing semi-colon after use Employee. The "my $person" line is taken as an import to request from Employee, and is executed at compile time in a scope all its own, so the rest of the program doesn't use a lexical $person, and the global $person isn't ever set.	[reply] [d/l] [select]
Re^3: Can't call method on an undefined value? by dragonchild (Archbishop) on Apr 11, 2005 at 17:22 UTC
However, the important points to note: strict makes the declaration for $name required, removing that as a possible problem. Global symbol "$person" requires explicit package name at test.pl line 5. makes it apparent that there's a problem with the declaration of $person. Once you know there's a problem with the declaration of $person, you look at that line and the line above. You quickly find the missing semi-colon. Hence, the readily-apparent comment. :-) My wife's blog	[reply]
Re^4: Can't call method on an undefined value? by ysth (Canon) on Apr 11, 2005 at 17:34 UTC
Re^5: Can't call method on an undefined value? by dragonchild (Archbishop) on Apr 11, 2005 at 17:37 UTC
Re: Can't call method on an undefined value? by borisz (Canon) on Apr 11, 2005 at 14:49 UTC
Your code should work fine, if you add a ; after `use Employee` and a `my` before `$name = $person->name;`. Boris	[reply]