Re: Module Proposal: Package::Data::Inheritable

Bill Ward ha scritto:
> On 9/4/07, Giacomo Cerrai <giantolo@xxxxxxxx> wrote:
> > A typical case I feel the need for that is when you have a hierarchy of
> > classes where you deal with a lot of data fields and you name them with
> > class data members:
> >
> >      our FIELDNAME1 = 'field1';
> >      our FIELDNAME2 = 'field2';
> >      ...
> >      our FIELDNAMEn = 'fieldn';
> >
> > and then you use them like this:
> >
> >      foo({param1 => $val,
> >           fields => { $FIELDNAME1 => $val1,
> >                       $FIELDNAME2 => $val2,
> >                       ...
> >                       $FIELDNAMEn => $valn,
> >                      },
> >           });
> >      ...
> >      foreach my $field ($FIELD4, $FIELD2, ..., $FIELD10) {
> >      ...
> >
> > With accessor methods this would be considerably more verbose:
> >
> >      foo({param  => $val,
> >           fields => { $SomeClass->FIELDNAME1 => $val1,
> >                       $SomeClass->FIELDNAME2 => $val2,
> >                       ...
> >                       $SomeClass->FIELDNAMEn => $valn,
> >                      },
> >           });
> >      ...
> >      foreach my $field ($SomeClass->FIELD4, $SomeClass->FIELD2, ...,
> > $SomeClass->FIELD10) {
> >      ...
> >
> > This becomes quickly unreadable and is not lazy.
> > Furthermore every fieldname access is a method call which is too much
> > overhead, especially when you have many fields to deal with.
>
> If you put the field names into an array (or hash) then it becomes a lot easier.
>
>       our @FIELDNAMES = ( ... );
>       sub fieldnames { @FIELDNAMES };
>
>       my %fields;
>       my @names = $SomeClass->fieldnames();
>       @fields{@FIELDNAMES} = ($val1, $val2, ..., $valn);
>       foo({param1 => $val, fields => \%fields );
>       ...
>       foreach my $field (@{$SomeClass->fieldnames()}) {
>       ...

The set of fields a statement works on is not always the same.
Notice that the fields passed to foo() and the fields used in the
foreach are different.

cheers,
Giacomo