package PriceType;
use base qw(Class::Singleton);

sub id { croak "this should return the price_type_id" };

my $dbh = DBI->connect(...);
my $price_type = $dbh->prepare('select price_type_id, price_type_label from price_type');
$price_type->execute;
$price_type->bind_columns(my \($id, $label) );
while (my $type = $price_type->fetch) {
    $label =~ = s/[^a-z]//gs;
    my $method = join('::', __PACKAGE__, $label, "id");
    my $id = $id;
    { no strict 'refs'; *{$method} = sub { $id } };
};

##</code><code>##

sub get_price {
   my ($self, $price_type) = @_;
   croak "need PriceType" unless UNIVERSAL::isa($price_type, 'PriceType');
   my $sth = $self->sql_find_price;
   $sth->execute($self->id, $price_type->id);
   my ($price) = $sth->fetchrow_array;
   return $price;
}

##</code><code>##

my $cost = $product->cost;
my $list = $product->list_price;
my $sale = $product->sale_price;

##</code><code>##

my $cost = $product->price(PriceType::Cost->instance);
my $list = $product->price(PriceType::ListPrice->instance);
my $sale = $product->price(PriceType::SalePrice->instance);

##</code><code>##

my $cost = PriceType::Cost->instance->get_price($product);
my $list = PriceType::ListPrice->instance->get_price($product);
my $sale = PriceType::SalePrice->instance->get_price($product);