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

hello,

I am using Conf.pm to get my config values. it is tidious to copy the same Conf.pm for each of my app and the only different is the config file path. so i would like to creat e a base Conf.pm and abstract out the config file part from sub load_config {}(probably by subclassing BaseConf) . this will allow me to provide different config path for different app easily. but i am not sure how to go about it.

the codes are based on the krang Conf.pm https://svn.krangcms.com/trunk/krang/lib/Krang/Conf.pm

anyway, here is my code 

package BaseConf;

use strict;
use warnings;

use Carp qw(croak);
use Config::Tiny;

my $Conf;

sub _load_config {
    my $conf_file = "/path/to/my.conf";
    croak "unable to find $conf_file" unless -e $conf_file and -r $con
+f_file;

    $Conf = Config::Tiny->read( $conf_file );
    croak "read config file '$conf_file' failed: $Config::Tiny::errstr
+" unless $Conf;
}
 
BEGIN { _load_config() }

sub get {
    croak "invalid method called $_[1]" if not exists $Conf->{_}->{ $_
+[1] };
    return $Conf->{_}->{ $_[1] };
}
 
sub import {
    my $pkg     = shift;
    my $callpkg = caller(0);

    foreach my $name (@_) {
        no strict 'refs';    # needed for glob refs
        *{"$callpkg\::$name"} = sub () { $pkg->get( $name ) };
    }
}
 
1;

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right now i can use it like 

use base BaseConf qw/name1 name2/;
...

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but i would like to have it subclassed.. maybe like this :

package MyConf;
use base BaseConf;

sub provide_my_config_path_here {}

package main;
use MyConf qw/name1 name2/;

[download]
ideas?

Replies are listed 'Best First'.
Re: need some OO help
by friedo (Prior) on Mar 26, 2007 at 16:45 UTC

    Just put an empty ("abstract") method in your base class, which your subclasses will use to get the path.

    package BaseConf;

my $Conf;

sub _load_config {
    my $self = shift;
    my $conf_file = $self->config_file_path;
    croak "unable to find $conf_file" 
      unless -e $conf_file and -r $conf_file;

    $Conf = Config::Tiny->read( $conf_file );
  croak "read config file '$conf_file' failed: $Config::Tiny::errstr" 
      unless $Conf;
}


sub config_file_path { 
    croak "config_file_path must be provided by subclass.";
}

...

package MyConf;

use base 'BaseConf';

sub config_file_path { 
    return '/path/to/conf.file';
}

    [download]
[reply]
[d/l]
      thanks. that should fix it except..

      since i am using BEGIN { _load_config() } in base class. how do i get around using the method you suggested?

[reply]
[d/l]

        Put it in your derived class instead (and turn it into a class method.)

        package MyConf;

...

BEGIN { 
    __PACKAGE__->_load_config;
}

        [download]

        That will call _load_config (as a method) in your parent class, which will call config_file_path in your child class.

[reply]
[d/l]
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