如何在Perl的Class :: DBI中覆盖自动生成的访问器？

Question

I followed the example at http://wiki.class-dbi.com/wiki/Overriding_autogenerated_accessors

I want to modify the URL before it is inserted to the database:

package Hosting::Company;
use base 'Class::DBI';

 my $class = __PACKAGE__;

$class->table('Companies');
$class->columns(Primary => 'CompanyId');
$class->columns(Others => qw/Name Url Comment/);

sub Url {
my $self = shift;

    # modify URL.
    if (@_) {
        $_[0] = 'aaaaaaaaaaaa';
        # return $self->_Url_accessor('aaaaaaaaaaaa'); - doesn't work either
    }

    # Back to normal Class::DBI 
    return $self->_Url_accessor(@_);
}

But it doesn't work:

my $company = Hosting::Company->insert({ Name => 'Test', Url => 'http://http://url' });
print $company->Url, "\n";

Shows:

http://http://url

I wish the Class:DBI mailing list were still alive!

Answer 1

In you URL accessor, you check whether a parameter was passed to that method. But you aren't passing anyhting in so the accessor will do nothing but call _Url_accessor(). You should probably call _Url_accessor first and then modify the result:

sub Url {
    my $self = shift;

    # Was there a param passed in?
    if ( @_ ) {
         # Do you really want to modify it here?
         return $self->_Url_accessor(@_);
    }
    else {
        my $url = $self->_Url_accessor();
        # mangle result here:
        $url = 'aaaaaaaaa';
        return $url;
     }
}

If you want to change the URL before it even goes in the database, I guess you must provide a normalize_column_values in your class and this will be called each time an insert is made.

Answer 2

Overriding an accessor does not change insert . The best way to handle data normalization is to override normalize_column_values() . But Manni is right, your accessor is busted.

PS The CDBI mailing list is still active, just hasn't seen much posting. Most have moved on to DBIx::Class .