Bill Ward ha scritto:
On 9/4/07, Giacomo Cerrai <[EMAIL PROTECTED]> 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 = $SomeClass->fieldnames();
@[EMAIL PROTECTED] = ($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
