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How can I create private object variables?

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Contributed by premchai21 on Mar 18, 2001 at 00:08 UTC
Q&A  > object-oriented programming


Answer: How can I create private object variables?
contributed by jeffa

Use closures. Check out perltoot for more info on how this code works.

{ package Foo; sub new { my $pkg = shift; my %data = ( bar => undef, ); bless sub { my $field = shift; @_ and $data{$field} = shift; $data{$field} }, $pkg } sub bar { my $self = shift; # the blessed closure $self->( 'bar', @_ ) } }
And use:
my $foo = new Foo; $foo->bar(42); # set it print $foo->bar; # get it
Answer: How can I create private object variables?
contributed by pemungkah

Inside-out classes are another nice way to do this. The data is held in a my (lexical) variable inside the class; all the outside world sees is an anonymous scalar which is blessed into the class. The methods can access the class lexicals (as long as they're defined within scope of the lexicals), but the outside world can't.

See Class::Std and Object::InsideOut for examples.

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