I'm porting a small Java application to Perl, using Class::Std. Now I have a class with a constructor that calls the superclass constructor with certain required fields filled in. An example in Perl might be: 
package myclass;
use Carp qw(croak);

sub new {
    my ($class, $value) = @_;

    croak "required value missing" if @_ == 1 or !$value;

    return bless \$value, $class;
}

package mysubclass;
use base qw(myclass);

sub new {
    my ($class) = @_;

    return bless $class->SUPER::new(23), $class;
}

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Now in Class::Std, superclass "constructors" (ie BUILD and START) are called automatically. However, there doesn't seem to be a way to set or override the arguments for a superclass in a subclass. I'd like to do something like this: 
package myclass;
use Class::Std;
my %value :ATTR( :init_arg<value> );

package mysubclass;
use base qw(myclass);

sub BUILD {
    my ($self, $ident, $args) = @_;
    $args->{value} = 23;
}

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This doesn't work. Even though Class::Std calls BUILD(), then initialises the object from the constructor arguments, and then calls START(), the third argument passed to each BUILD/START method is specific to that method - its discarded afterwards. There doesn't seem to be any way to influence the arguments in this way. Doing this: 
mysubclass->new;

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gives: 
Missing initializer label for myclass: 'value'.
Fatal error in constructor call

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Anyone got any ideas before I open a ticket in RT?

Cheers,
Rob.

In reply to Overriding arguments in Class::Std superclass constructors by fce2

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