Re: Trigger before/around/after stuff

On Tue, Jul 22, 2008 at 10:18 AM, Paul Driver <[email protected]> wrote:
> I think the major benefit of the "around" trigger was being able to filter
> the value going into the setter.  I don't have any use case for 'before'
> that couldn't be accomplished with older "standard" (after) triggers - so
> some kind of setter-filter (needs a better name) would probably do just as
> well.  That could be done by a MooseX, potentially.

Anything that depends on the old value would be a use case for
"before". For example, one of my uses would be:

has type => (
    trigger => {
        before => sub {
            $registry->unregister_tile_by_type($_[0], $_[1]);
        },
        after => sub {
            $registry->register_tile_by_type($_[0], $_[1]);
        },
    },
);

before is also useful for additional validation. You want to throw the
exception *before* you set an invalid value.

Shawn