I have a plain old module that I wrote before I was conversant with Perl OO.
It provides a several subroutines, which I call from many scripts, built up over several years.

At present, I want to morph my module to OO (so that each instance can have a state which is accessible to all subs). However, I want to morph the module in a such way that my old scripts continue to work, and that my new scripts can use the OO syntax and other goodies. I found one way to do this, shown below on a very simple example.

Learned monks, I would like to see your comments on other, perhaps better ways to achieve my goal.

MyModule before the change 

#! perl -w

use strict;
package MyModule;

sub isFile {
    my $file = shift;     # a file in local directory expected    
    my $verbose = shift;     # optional    
    if (! -f $file) {
        print STDERR "*** no such file $file in current directory\n";
        return 0;
    }
    else {
        print STDERR "... isFile $file\n" if $verbose;
        return 1;
    }
}

# more subs ...

1;

[download]
A test script, before the change 
#! perl -w
use strict;

use MyModule;

# before change to OO and after

MyModule::isFile("MyModuleTest.pl");
MyModule::isFile("NotHere");

[download]

MyModule after the change 

#! perl -w

use strict;
package MyModule;

sub new {
    my ($class, %args) = @_;
    my $self = {
        class           => $class,
        verbose         => $args{verbose} || 0,
        otheropt        => $args{otheropt} || 0,
    };
    bless $self, $class;
    return $self;
}

sub isFile {
    my $self = shift if ref $_[0] && ref $_[0] eq $_[0]->{class};
    my $file = shift;   # a file in current directory expected  
    if (! -f $file) {
        print STDERR "*** $file: file not found in current directory\n
+";
        return 0;
    }
    else {
        print STDERR "... $file: file found in current directory\n" if
+ $self->{verbose};
        return 1;
    }
}

# more subs ...

1;

[download]

A test script, after the change 

#! perl -w
use strict;

use MyModule;

# works before change to OO and after

MyModule::isFile("MyModuleTest.pl");
MyModule::isFile("NotHere");

# works after change to OO

my $mod = MyModule->new;

$mod->isFile("MyModuleTest.pl");
$mod->isFile("NotHere");

$mod = MyModule->new( verbose => 1 );

$mod->isFile("MyModuleTest.pl");
$mod->isFile("NotHere");

[download]
rudif

In reply to How to morph a plain module to OO by Rudif

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