On 11/03/2006 02:23 AM, Muttley Meen wrote:
Hi!
Sorry if I double post, but the maillserver seems to have something against
perl scripts attachements, so my first email was droped by the MTA : /
Maybe if I put the code inline will be ok
In the attached script I implement two packages:
Package1 and Package2.
Package2 is derived from Package1, which I guess I dont well.
Now Package1 has a method called IncErr which increments a variable
named $err.
If I call something like:
$a = Package1::new();
$a->IncErr();
print "ERR1: $a->{err}\n"; # should print 1
all goes well, but if I call something like:
$a = Package1::new();
$a->Package2->Create(); # this should call IncErr too
This is not allowed because "Package2" is not a method within the class
Package1. You want this:
my $b = Package2->new();
$b->Create();
print "ERR(\$b): $b->{err}\n";
print "ERR1: $a->{err}\n"; # should print 1
doent't work as I expected.
Is there something wrong with the way I `bless`-ed the class Package2 ?
------>8-----------
#! /usr/bin/perl
use strict;
use warnings;
# Modify your program to work with these.
package Package1 ;
sub new {
my ($class) = @_;
$class = __PACKAGE__ ;
print "Call new [".$class."]\n" ;
$r = [];
$this = {};
$class->{err} = 0 ;
$r->[0] = Package2::new($this->{sock_fd} );
bless $this, $class;
return $this ;
}
sub IncErr {
my $this = shift ;
$this->{err} += 1 ;
}
sub Package2 {
my $this = shift ;
@_ ? ($r->[0] = shift) : $r->[0];
}
package Package2 ;
@ISA = ("Package1");
sub new {
my ( $this, $sock ) = @_ ;
$class = __PACKAGE__ unless @_;
$this->{sock_fd} = $sock ;
bless $this;
return $this ;
}
sub Create {
my $this = shift;
print "Call Create\n" ;
print "ERR2: $this->{err} ( this should print 2 )\n" ;
$this->IncErr() ;
print "ERR2: $this->{err} ( this should print 3 )\n" ;
}
my $a = Package1::new();
$a->IncErr();
$a->IncErr();
$a->Package2->Create();
print "ERR1: $a->{err} ( this should print 3 )\n" ;
------------------->8--------------------
I didn't look in detail at your program, but I also see that you use a
suboptimal syntax for creating objects; don't use "::"; use "->", e.g.
my $a = Package1->new();
Using "::" will work, but it creates problems that will make you
sad--such as preventing inheritance.
Using "use strict" and "use warnings" will help you catch errors like
the one above where you do "$a->Package2->Create()"
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