http://www.perlmonks.org?node_id=576716


in reply to Better Inside-Out Objects :)

You don't seem to really want "inside-out" objects -- you seem to want encapsulated objects. Inside-out is just one way of doing that and it seems like you're going out of your way to try to make it act like something else.

A couple quick observations:

I'll let you know if more things occur to me later.

Update

The more I think about it, the more this just seems like a way of disguising an accessor call by way of overloading.

And there's no reason the trick requires inside-out objects. Here's a plain-old blessed hash version -- and it still gives you package-specific hash values that don't collide:

SmartHash.pm

package SmartHash; use strict; use warnings; use Carp; use overload "%{}" => sub { my $caller = caller; croak "Illegal object access" unless $caller->isa(__PACKAGE__) +; return shift if $caller eq __PACKAGE__; return shift->{$caller} ||= {}; }, fallback => 1; 1;

Foo.pm

package Foo; use strict; use warnings; use base 'SmartHash'; sub new { my $class = shift; bless {}, $class; } sub foo { my $self = shift; $self->{foo} = shift if @_; return $self->{foo}; } 1;

Bar.pm

package Bar; use strict; use warnings; use base 'Foo'; sub bar { my $self = shift; $self->{bar} = shift if @_; return $self->{bar}; } sub foo { my $self = shift; $self->{foo} = shift if @_; return $self->{foo}; } 1;

testbar.t

use strict; use warnings; use Test::More tests => 9; use Test::Exception; require_ok( 'Bar' ); require_ok( 'Foo' ); my $o = Bar->new; my $p = Foo->new; dies_ok { $o->{bar} = 42 } "dies on direct access"; $o->bar(13); is( $o->bar, 13, "Bar obj set/get bar" ); $o->foo(42); is( $o->foo, 42, "Bar obj set/get Bar's foo" ); $o->Foo::foo(23); is( $o->Foo::foo, 23, "Bar obj set/get Foo's foo" ); $p->foo(99); is( $p->foo, 99, "Foo obj set/get foo"); is( $o->foo, 42, "Bar obj's foo is still Bar obj's foo" ); is( $o->Foo::foo, 23, "Bar obj's Foo's foo is still Bar obj's Foo's fo +o" );

prove -v testbar.t

testfoo....1..9 ok 1 - require Bar; ok 2 - require Foo; ok 3 - dies on direct access ok 4 - Bar obj set/get bar ok 5 - Bar obj set/get Bar's foo ok 6 - Bar obj set/get Foo's foo ok 7 - Foo obj set/get foo ok 8 - Bar obj's foo is still Bar obj's foo ok 9 - Bar obj's Foo's foo is still Bar obj's Foo's foo ok All tests successful. Files=1, Tests=9, 0 wallclock secs ( 0.00 cusr + 0.00 csys = 0.00 C +PU)

I guess I'm not clear on what you find so difficult about inside-out objects (assuming a sane inside-out class generator to handle destruction, serialization, threads, etc.). Is "$foo{ id $self }" so much more difficult than "$self->{foo}"? Or even "$self->foo()"?

What are you trying to optimize for? The hash-based interface does avoid having to pre-declare any properties -- you can just say "$self->{baz}" and the "baz" property springs into existence. That comes at the cost of the typo checking.

I can also see a use for it if you're trying to upgrade legacy code. You can just drop "use base 'Encapsulate'" into your object modules and they should continue working like normal without having to edit anything else there, but everything else external that accesses objects will break.

But just as is, this feels close to an XY Problem to me.

-xdg

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