for my $attr (qw( country customer_number ticket_type )) {
    my $reader  = "get_$attr";
    my $clearer = "clear_$attr";
    has $attr => (
            is        => 'rw',
            reader    => $reader,
            writer    => "set_$attr",
            predicate => "has_$attr",
            clearer   => $clearer,
            trigger   => sub {
                my ($self)  = @_;
                if (! defined $self->$reader || $self->$reader eq '' ) {
                    $self->$clearer;
                }
            }
    );
}