SPUG: Question: scoping

Ronald J Kimball rjk-spug at tamias.net
Mon Sep 15 14:42:25 PDT 2008

On Mon, Sep 15, 2008 at 01:11:02PM -0800, Christopher Howard wrote:
> When I run this, I get "Can't call method "value" without a package or 
> object reference at ./main.pl line 13." from the interpreter.  I was a 
> bit confused, so I put constructor and de-constructor registration code 
> into MyClass, to track was was happening to the objects.
> From what I can tell, the objects are getting destroyed before they 
> leave the scope of the first for loop.  This leaves me still confused, 
> because I declared @obj outside of the scopes of the for loops.

Works for me.  I suspect the problem is that MyClass's new method is not
actually returning the blessed reference.

> Obviously I could solve the immediate problem by putting them both in 
> the same for loop.  But what I really want is to understand why the 
> objects are going out of scope before I think they should be.

So, did you actually try that yet...?  :)


P.S.  Here's the code and I ran, and the output:

#!/usr/bin/env perl
use strict;
use warnings;

my @obj;

for(my $i = 0; $i<10; $i++) {
   $obj[$i] = new MyClass;

for(my $i = 0; $i<10; $i++) {
   $obj[$i]->value("Test Value.");


package MyClass;

sub new {
  return bless {}, shift;

sub value {
  print "@_\n";


MyClass=HASH(0x811f27c) Test Value.
MyClass=HASH(0x811fa50) Test Value.
MyClass=HASH(0x814496c) Test Value.
MyClass=HASH(0x8144960) Test Value.
MyClass=HASH(0x8144024) Test Value.
MyClass=HASH(0x814400c) Test Value.
MyClass=HASH(0x814cfd8) Test Value.
MyClass=HASH(0x814cfc0) Test Value.
MyClass=HASH(0x814cfa8) Test Value.
MyClass=HASH(0x814cf90) Test Value.

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