Some time ago (nearly 15 years, actually) in this thread, btrott was talking about various ways of protecting a blessed object and quite a lot of discussion came from it.

I haven't seen anyone suggest using Variable::Magic to achieve this. I'm thinking of writing a base class with a class method on the lines of this.

sub new
{
    my $class = shift;
    my %params = @_;
    my $protected = sub {
        croak qq{Attempt to access protected data "$_[2]"} unless call
+er->isa(__PACKAGE__);
    };
    my $wiz = wizard(
        store   => $protected,
        fetch   => $protected,
        exists   => $protected,
        delete   => $protected,
    );
    my %self;
    cast %self, $wiz;
    my $self = \%self;
    bless $self, $class;
    $self->$_($params{$_}) foreach keys %params;
    return $self;
}

[download]

Does anyone have any views on whether this (a) will work correctly and (b) will be useful? The intention is to make the underlying hash inaccessable other than to subclasses of a class using this as a parent.

The main problem I'm trying to solve is the programmer who accidentally types $obj->{field} when he meant $obj->field, thereby inadvertantly bypassing any clever stuff in the getter.

In reply to Private & Protected Objects by Sixes

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