Re: Accessor methods questions

Moin Gunnar!

Gunnar Strand schrieb am 21.08.2011 um 22:27 (+0200):

> has 'weight' => (
> is => 'ro',
> writer => '_set_weight',
> );

> 1. The above gives me the impression that the accessor method
> *replaces*(i.e., renames) the accessor methods.

By default, there would be weight() acting as getter/setter (or
reader/writer). By specifying "_set_weight" for the writer, you'll
get weight() as a getter and _set_weight() as a writer.

> What is not clear is how accessor write methods store the value if I
> have
> 
> "foo => (is => 'rw', writer => 'set_foo')"

They store it in $self->{foo} because that's the name of the property.

> 2. The above example in the manual shows a way to make an attribute
> "publicly readable, but privately settable", but I don't see how the
> "_set_weight" method can store the weight value?

Basically:

  my $self = shift;
  $self->{weight} = shift;

I didn't understand all of your questions, so my answer might not help
you. Maybe if you run this little script:

          \,,,/
          (o o)
------oOOo-(_)-oOOo------ demo.pl ----
package Bla;
use Moose;
has 'blub', is => 'rw', writer => '_set_kram';
has 'blog', is => 'rw';
no Moose; # without this line left-over symbols in the symbol table

package main;
use Data::Dumper;
use feature 'say';
say for sort keys %Bla:: ; # print package symbol table keys
say '-' x 66;
my $bla = Bla->new( blub => 99, moin => 88 );
# "moin" ignored, not a registered attribute
# $bla->blub(44); # read-only
print Dumper $bla;
$bla->_set_kram(44);
print Dumper $bla;


You can see that in addition to "blub" and "blog", a entry "_set_kram"
is generated in the symbol table. Just one subroutine in addition.
And $bla->blub( $val ) will fail with "Cannot assign a value to a
read-only accessor".

-- 
Michael Ludwig