in reply to OO - problem with inheritance

You could use a method instead of variable to store information about parameters. This way this information could be overridden easily in subclasses: 

my $parameter_config = {
        mandatory  => {type    => 'boolean',
                       default => 0,
                       valid   => 0},
                       };

sub parameter_config { $parameter_config };

sub valid_parameter {
    my $class = shift;

    my @param = @_;
    foreach (@param) {
        my $param_config = $class->parameter_config->{$_};
        if ($param_config) {
            $param_config->{valid} = 1;
        } else {
            die "Parameter $_ not known";
        }
    }
    return 1;
}

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And in your classes you should call valid_parameter as method: 

Integer->valid_parameter(qw(mandatory));

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Subclasses which need other configuration of parameters just override method parameter_config.

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

Replies are listed 'Best First'.
Re: Re: OO - problem with inheritance
by uwevoelker (Pilgrim) on Jan 14, 2002 at 20:30 UTC
    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});

    [download]
    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));
}

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    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 }

    [download]
    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
[reply]
[d/l]
[select]
      my $parameter_config = __PACKAGE__->SUPER::parameter_config;
$parameter_config->{max_length}{max} = 255;
$parameter_config->{max_length}{default} = 255;

sub parameter_config { $parameter_config }

      [download]
      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 }

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

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

[reply]
[d/l]
[select]
        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.
[reply]
        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; }

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        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
[reply]
[d/l]

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