On Sat, Feb 22, 2014 at 12:46 AM, Aria Stewart wrote:
> On Fri, Feb 21, 2014 at 07:37:34PM -0800, Jan Krems wrote:
> > For me one of the most powerful things about promises is that they can
be
> > passed around, returned from functions, etc.. It seems like your way of
> > handlings errors prevents this. Or at least makes it very dangerous
Perfectly safe unless you want to reenter the event loop before you
> actually deal with them. Which, yes, generators. Actually, this makes
> me think that for promisables anyway, attaching a catch after
> reentering the event loop should probably be an error. Possibly
> attaching any then/catch/finally/() actually. Hmm...
>
I agree that this does remove some of the purity of the basic premise
> of futures/promises, but I'm not sure it actually causes practical
> issues.
> Why not
>
> function appendComment(id) {
> var user = db.load('user'),
> thread = db.load('thread'),
> comments = thread.thenPromise(function(R, th) {
R(th.getComments()); });
>
> return [user, thread, comments];
> }
>
> instead, returning the promises -- no generator. If you're deferring error
> handling to the caller, do it completely rather than mixing modes?
I would rewrite the original as:
>
function appendComment(id) {
var user = dbHandle.load('user', { id: 'jen' });
var thread = dbHandle.load('thread', { id: 1 });
> return thread.getComments().then(function(comments){
> // more code
> });
> }
> appendComment(23)
> .catch(function(E){ /* do something with error */ )};
> But it is a good point: promises that force you to handle errors don't
play
> that nicely when you enter the event loop before setting up the error
handling.
> What would your use case there be? What would error handling look like if
you
> used non-enforcing promises?
As Aria says, outside of generators, I'd be very interested in hearing
> a use case for then/catch/etc on nextTick. Unsurprisingly, to me, it
sounds harmful not helpful. =p
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