How do I convert subroutines to an object/package in perl / perl5? - oop

Question

main.pl:
#!/usr/bin/perl
use strict;
use warnings;
use v5.14;
use ReadData;
my $read = ReadData->new();
my #name = $read->getNames();
$read->printNames(#name);
ReadData.pm:
#!/usr/bin/perl
package ReadData;
use strict;
use warnings;
use v5.14;
#
sub new {
my $class = shift;
my $self = {};
bless $self, $class;
return($self);
}
sub getNames {
# read in data
my #data;
print "\nName of first matrix? ";
chomp($data[0] = <>);
print "\nName of second matrix? ";
chomp($data[1] = <>);
return(#data);
}
sub printNames {
my #name = #_;
print "\nname1: " . $name[0];
print "\nname2: " . $name[1];
}
1;
I have these subroutines in another version of the main program, and everything works fine there. I don't call the object, and the input names are reflected correctly in the output as seen bleow:
my #name = getNames();
printNames(#name);
sub getNames { same as above . . . }
sub printNames{ same as above . . . }
The code I have pasted at the very top technically WORKS, because it runs, and gives output, but the output is incorrect.
When I enter "A" as the first name, and "B" as the second name, this is what I get back:
>>> perl alt.pl
Name of first matrix? A
Name of second matrix? B
name1: ReadData=HASH(0x1d082f0)
name2: A
Can anyone help me to fix this? I've been reading like 50 perl tutorials online and I can't wrap my brain around what I'm supposed to be doing. My only other real programming experience is OOP in Java, and I don't follow this perl constructor stuff . . .

Answer 1

I think the main thing you're missing is that when you call a method on an object:
$read->printNames(#name);
the object itself ($read) is passed into the method (printNames) as the first argument, before all the regular arguments. (In Java this happens implicitly — the object is just magically made available as this — but in Perl it's explicit — the object is $_[0].) So, you can change printNames to this:
sub printNames {
my $this = shift;
my #name = #_;
print "\nname1: " . $name[0];
print "\nname2: " . $name[1];
}
(Of course, in Perl, as in Java, it's more usual for instance methods to have something to do with the object. Your printNames method is strange in that it never uses $this at all. But this should get you started.)

Answer 2

You probably want to store the data within the object rather than copying it back and forth:
alt.pl:
#!/usr/bin/perl
use strict;
use warnings;
use ReadData;
my $read = ReadData->new();
$read->getNames();
$read->printNames();
ReadData.pm:
package ReadData;
use strict;
use warnings;
#
sub new {
my $class = shift;
my $self = {};
bless $self, $class;
return($self);
}
sub getNames {
my $self = shift;
# read in data
print "\nName of first matrix? ";
chomp($self->{name1} = <>);
print "\nName of second matrix? ";
chomp($self->{name2} = <>);
return;
}
sub printNames {
my $self = shift;
print "\nname1: " . $self->{name1};
print "\nname2: " . $self->{name2};
}
1;