Re: Re: OO - problem with inheritance

[uwevoelker]

Hello Ilya,
thank you for your fast answer. Did I got you right, that when I want to change other configuration parameters like this

&CCS::Data::Datatype::base_class::config_parameter(
        max_length => {max => 255, default => 255},
        min_length => {max => 255});

which is taken from my String class, I need to override your sub parameter_config in this way?

sub parameter_config {
    return {max_length => {max => 255, default =>255));
}

But I also need the other parameters from base class (like min => 0 and valid => 0 in this case).

Or could I do something like this:

my $parameter_config = SUPER->parameter_config;
$parameter_config->{max_length}{max} = 255;
$parameter_config->{max_length}{default} = 255;

sub parameter_config { $parameter_config }

My classes not only inherit from base_class.pm. There are also datatypes that inherit from other datatypes. Such as Text inherits from String (but no direct base_class) and PrimaryKey inherits from Integer. Is such inheritance with one of this configuration methods combineable?

My goal is, that I can add new parameters only in base_class (let's say has_double_letters or max_number / min_number) and all the datatypes need only to "activate" this new parameters via the ->valid_parameter(qw(mandatory max_number)) call.

Thanks, Uwe

[IlyaM]

my $parameter_config = __PACKAGE__->SUPER::parameter_config;
$parameter_config->{max_length}{max} = 255;
$parameter_config->{max_length}{default} = 255;

sub parameter_config { $parameter_config }

This should work if you want to register your parameters in base_class. BTW you don't need to override parameter_config at all in this case because SUPER->parameter_config returns hash reference stored in $parameter_config variable in base class. So next two lines do affect hash used by base_class. If it is not desired effect you should clone that hash:

use Storable qw(dclone);

my $parameter_config = dclone(__PACKAGE__->SUPER::parameter_config);
$parameter_config->{max_length}{max} = 255;
$parameter_config->{max_length}{default} = 255;

sub parameter_config { $parameter_config }

Update: Fixed usage of wrong syntax (SUPER->method instead of __PACKAGE__->SUPER::method)

--
Ilya Martynov (http://martynov.org/)

[uwevoelker]

The hash would need to be cloned. But I have an other idea - see my other posting titled "new idea - please comment on this".
Thanks.

[uwevoelker]

Hello Ilya,
I need your help. I have written an Parameter::Validate module. And now I would like to use it as you said.

use strict;
use lib  '/home/uwe/cvs/perl';
use lib  '/home/uwe/cvs/perl/module';
use Parameter::Validate;
use base 'CCS::Data::Datatype::base_class';

# parameter configuration
#my $pv = CCS::Data::Datatype::base_class->pv->clone;
my $pv = SUPER->pv->clone;
$pv->enable(qw(mandatory min_length max_length));
$pv->change(max_length => {max => 255, default => 255},
            min_length => {max => 255});
sub pv { $pv; }

If I use the full qualified parent class name (CCS::Data::Datatype::base_class->pv) everything works like expected. But if I use the line with SUPER->pv I get an error: Can't locate object method "pv" via package "SUPER" (perhaps you forgot to load "SUPER"?) at /home/uwe/cvs/perl/CCS/Data/Datatype/String.pm line 16.
So, what is wrong with SUPER?

Thank you, Uwe

[IlyaM]

I'm sorry I gave you example which uses wrong syntax. See updated node for fix. Instead of SUPER->pv it should be YourPackage->SUPER::pv. Here YourPackage is full qualified name of your subclassed package. Also you can use special token __PACKAGE__ instead of YourPackage. It will be substituted by Perl with this name.

BTW be careful with selection of package name. FYI CPAN already has Params::Validate. It is not same name but very close.

--
Ilya Martynov (http://martynov.org/)