twine

Untangle and wrap together your async

Async code gets tangled. npm install twine.

{asyncfn,sync,future}:Twine = require \twine
 
class Example extends Twine
    getdata: asyncfn ->
        # sync code to get some data
 
    makefolder: asyncfn ->
        # sync code to create a directory to store a file in
        # this is run at the same time as getting the data
 
    writefile: @depends \getdata \makefolder asyncfn ({getdata: data, makefolder: folder})->
        # once there is some data and the directory exists,
        # write the data to a file in the directory
        return filename
 
    emaillink: @depends \writefile asyncfn (results)->
        # once the file is written let's email a link to it...
        # results.writefile contains the filename returned by writefile.
 
ex = new Example
ex.emaillink (err,results)->console.error that if err?

Twine ties in async.js's async.auto and node-sync so you can write clean, uncluttered, modular async code.

Any method in a subclass of Twine can be dependency, so long as it's either an asyncfn or takes a Node-style (err,result)-> callback. Methods declare their dependencies using Twine.depends. When you call a method with dependencies, Twine unwraps them and hands over to async.auto, which does some clever stuff to work out when to call the things.

Anywhere within an asyncfn asynchronous functions can be called synchronously using sync:

asyncfn ->
    try
        contents = (sync fs.read-file) "awesome.txt" \utf8
    catch err

Errors what would have got passed to the first argument of the callback get thrown.

MIT. ©2013 Matt Brennan.