On 4/4/07 12:05 PM, Ovid wrote:
> Note the 'return' condition. I found that if I didn't have that in,
> the following would throw an exception:
>
> my $os = Donhost::OS->new( os => 'ubuntu' );
>
> The hack guarantees that only things like the following throwing
> exceptions:
>
> $os->os('windows');
> $os->description('sucks');
>
> The hack relies on the order of call stack frames being different when
> I'm constructing an object or just setting an accessor directly. How
> can I do this without relying on the internals like this?
The problem is that this:
$o = Foo->new(a => 123)
is really this:
$o = Foo->new;
$o->a(123);
The only way to distinguish the two is by calling context. That said, there
are (slightly) better ways to detect the context than using caller().
Here's what I suggest:
# Override init in you common base class
# (See the Rose::Object docs for details)
sub init
{
my($self) = shift;
local $self->{'__allow_set'} = 1; # or whatever attr name you pick
$self->SUPER::init(@_);
}
Then, in your trigger, replace this:
my ($called_from) = caller(1);
return if $called_from eq 'Rose::Object';
with this:
return if shift->{'__allow_set'};
Granted, this is still a bit of a hack, but at least it only relies on
public APIs, rather than internal implementation details.
-John
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