path: root/posts/2009-06-30-private-and-protected-methods-with-moose.org

Yesterday, one of our interns asked me a question about private method
in Moose. I told him that for Moose as for Perl, there is no such things
as private method. By convention, methods prefixed with '\_' are
considered private.

But I was curious to see if it would be something complicated to
implement in Moose. First, I've started to look at how the 'augment'
keyword is done. I've then hacked Moose directly to add the private
keyword. After asking advice to nothingmuch, he recommended me that I
implement this in a MooseX::* module instead. The result is here.

From the synopsis, MooseX::MethodPrivate do:

#+BEGIN_SRC perl
    package Foo;
    use MooseX::MethodPrivate;

    private 'foo' => sub {
    };

    protected 'bar' => sub {
    };


    my $foo = Foo->new;
    $foo->foo;    # die, can't call foo because it's a private method
    $foo->bar;    # die, can't call bar because it's a protected method

    package Bar;
    use MooseX::MethodPrivate;
    extends qw/Foo/;

    sub baz {
        my $self = shift;
        $self->foo;    #die, can't call foo because it's a private method
        $self->bar;    # ok, can call this method because we extends Foo and
        # it's a protected method
    }
#+END_SRC

I was surprised to see how easy it's to extend Moose syntax. All I've
done was this:

#+BEGIN_SRC perl
        Moose::Exporter->setup_import_methods(
            with_caller => [qw( private protected )],);
#+END_SRC

and write the =private= and =protected= sub. I'm sure there is some
stuff I can do to improve this, but for a first test, I'm happy with the
result and still amazed how easy it was to add this two keywords.