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), $class;
}
Now in Class::Std, superclass "constructors" (ie BUILD and START) are called automatically. However, there doesn't seem to be a way to set or override the arguments for a superclass in a subclass.
I'd like to do something like this:
package myclass;
use Class::Std;
my %value :ATTR( :init_arg<value> );
package mysubclass;
use base qw(myclass);
sub BUILD {
my ($self, $ident, $args) = @_;
$args->{value} = 23;
}
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;
gives:
Missing initializer label for myclass: 'value'.
Fatal error in constructor call
Anyone got any ideas before I open a ticket in RT?
Cheers,
Rob.