Re: Moose Question

Christopher,

I am not sure I am understanding the error you are describing. Could  
you write up a small failing test for me?

Thanks,

- Stevan

On Mar 27, 2008, at 3:09 PM, Christopher Brown wrote:
> Paul and Stevan,
>
> Sorry for the late reply.  Thanks for both answers.  Stevan, I am rely
> impressed with the rapidity of which you and the other Moose members
> respond.  I am also impressed with you presenting a working  
> prototype of my
> problem in as little time and code as you did.  It is really a  
> testament to
> Moose's power.
>
> In the end, I went with the solution that Paul offered.  That is, *
> create_anon_class()->rebless_instance*.   And, I have used this  
> recipe  a
> half-dozen or times since.   It is really powerful technique for  
> installing
> instance methods.  I did run into a snag with reblessing  
> instances.  It
> seems that I cannot access the meta object after reblessing.   I am  
> not so
> sure why I have the following work on the reblessed object:
>
>    $self->meta->add_method( 'test', sub { say "Hello World" } );     
> # $self
> is the reblessed self.
>
> Interestingly enough, the method does not produce an error.
>
> As I am discovering with Moose, there is probably a real simple and  
> elegant
> solutions of which has eluded me.  As always, your help is greatly
> appreciated.
>
> Best,
>
> Chris
>
>
>
>
>
>
> On Thu, Mar 20, 2008 at 8:22 AM, Paul Driver <[email protected]>
> wrote:
>
>> Chris,
>>
>> If you want to add generated methods to the class, it's
>> __PACKAGE__->meta->add_method(foobar => sub { print "Foo, bar! 
>> \n" });  I
>> don't think you want to do this in BUILD though - just at class  
>> compile
>> time.  I do this a lot when I have a bunch of similar methods and  
>> don't want
>> to repeat myself.
>>
>> If you want to add methods to a particular instance ONLY, the  
>> thing to do
>> is to create an anonymous subclass and rebless your instance to that
>> subclass, and add the methods to the subclass.
>>
>> Some example code - at BUILD time, add a method named $word that  
>> does say
>> $word for every word passed into the constructor.
>>
>> ---
>>
>> use feature q(say);
>> package Speaker;
>> use Moose;
>>
>> has words => (
>>        is => 'ro',
>>        isa => 'ArrayRef[Str]',
>>        predicate => 'has_words',
>> );
>>
>> # All Speakers know how to say bar
>> sub bar {
>>        say 'bar';
>> }
>>
>> sub BUILD {
>>        my ($self, $args) = @_;
>>        if ($self->has_words) {
>>                my %methods = map {
>>                        my $word = $_;
>>                        ($word => sub { say $word})
>>                } @{$self->words};
>>
>>                $self->meta->create_anon_class(
>>                        superclasses => [__PACKAGE__],
>>                        methods      => \%methods,
>>                )->rebless_instance($self);
>>        }
>> }
>>
>> package main;
>> my $a = Speaker->new;
>> my $b = Speaker->new(words => [qw(baz qux)]);
>> $a->bar; # => "Bar"
>> $b->bar; # => "Bar"
>> $b->qux; # => "Qux"
>> say "A" if $a->isa('Speaker'); # => "A"
>> say "B" if $b->isa('Speaker'); # => "B"
>> $a->qux; # Can't locate method "qux" via class "Speaker"
>>
>> ----
>>
>>
>> On Mar 19, 2008, at 4:22 PM, Christopher Brown wrote:
>>
>>  Dave,
>>>
>>> Sorry for taking so long to thank you for your reply.  Thanks.  On
>>> further
>>> t, it was a silly question, using a plain old method is obviously  
>>> the
>>> solution.
>>>
>>> I do have follow-up questions, though.  Suppose I want to  
>>> generate those
>>> plain old methods dynamically.  Is there a simple, moose way to  
>>> do this
>>> in
>>> the BUILD subroutine.   On e way to accomplish this is to assign an
>>> anonymous subroutine to a glob.  Like this:
>>>
>>> package My::App;
>>>
>>> use Moose;
>>> has name => ( is => 'rw', isa=>'Str' );
>>>
>>> sub BUILD {
>>>        **__PACKAGE__::method = sub { print "hello world\n"; } ;*
>>> }
>>>
>>> package main;
>>> my $app = My::App->new( { name => 'Moose' } );
>>> $app->method;
>>>
>>>
>>> But I don't want to do that.  I want to do it the Moose way.
>>>
>>> I can hear you ask, but why would you want to do that?  Well  
>>> suppose, I
>>> create an object that wraps a query.  If I can iterate over the  
>>> record
>>> set I
>>> can replace the data slot with the new record and still named  
>>> methods
>>> that
>>> act as accessors to the record.  This beats the snot out of  
>>> trying to
>>> instanciate a row object for each record.
>>>
>>> Thanks in Advance,
>>>
>>> Chris
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Mar 12, 2008 at 2:41 PM, Dave Rolsky <[email protected]>  
>>> wrote:
>>>
>>>  On Wed, 12 Mar 2008, Christopher Brown wrote:
>>>>
>>>>  Despite the 'lazy' evaluation, it appears as if the attribute  
>>>> value
>>>>> is
>>>>>
>>>> being
>>>>
>>>>> cached instead of being re-evaluated when the accessor is being
>>>>> called.
>>>>>
>>>>
>>>> Lazy just means "don't generate the attribute from the default sub
>>>> until
>>>> the _first_ time it is requested". It's still cached.
>>>>
>>>> If you want to return a different value each time then you just  
>>>> want a
>>>> plain old method, not an attribute.
>>>>
>>>>
>>>> -dave
>>>>
>>>> /*==========================
>>>> VegGuide.Org
>>>> Your guide to all that's veg
>>>> ==========================*/
>>>>
>>>>
>>