Iced coffee script with multiple callbacks - coffeescript

Question

I'm using Iced coffescript with upshot js when I am refreshing multiple data sources. The refresh method has TWo call backs one for success and one for error and I want to wait for each call to make either callback.
I can't see how to do this with idced coffescript without making an additional function. My question is - is there a more elegant way that I can defer to one of multiple callbacks?
This is the code I have currently:
refreshMe = (key, value, result) =>
value.refresh(
(success)=>
result success
,
(fail, reason, error)=>
result undefined, fail
)
#refresh = () =>
success={}
fail={}
await
for key, value of #dataSources
refreshMe key, value, defer success[key], fail[key]

Answer 1

This is the only way I have found to do it too. I'm using it in Backbone and wrap (for example) a model's #save function with an #icedSave:
# An IcedCoffeescript friendly version of save
icedSave: (callback) ->
#save {},
success: (model, response) -> callback(true, model, response)
error: (model, response) -> callback(false, model, response)

Answer 2

Here's some code I use for converting Promises .then (-> onSuccess), (-> onError) to errbacks (err, result) ->:
# You can write like this:
await value.refresh esc defer e, result
# onError - function to be called when promise rejected.
# onSuccess - function to be called when promise is fulfilled.
module.exports = esc = (onError, onSuccess) ->
util = require 'util'
return (result) ->
if util.isError result
# Always send back an error to first handler.
onError? result
else if onSuccess?
console.log onSuccess, result
# `await fn esc done, defer result`
onSuccess? result
else
# `await fn esc done`
onError? null, result
You could modify the esc function a bit to handle multiple arguments for each callback.

Answer 3

iced.Rendezvous lib is made explicitly for this case: return at the first of multiple callbacks. From the docs:
Here is an example that shows off the different inputs and outputs of
a Rendezvous. It does two parallel DNS lookups, and reports only when
the first returns:
hosts = [ "okcupid.com", "google.com" ];
ips = errs = []
rv = new iced.Rendezvous
for h,i in hosts
dns.resolve hosts[i], rv.id(i).defer errs[i], ips[i]
await rv.wait defer which
console.log "#{hosts[which]} -> #{ips[which]}"