Chain: a utility function for avoiding callback hell

[airstruck]

Have some code that looks like this?

Code: Select all

print 'fading in'
Timer.add(1, function ()
    print 'showing splash screen'
    Timer.add(1, function ()
        print 'showing title screen'
        Timer.add(1, function ()
            print 'playing demo'
        end)
    end)
end)

Oh no, callback hell. Use Chain to avoid deeply nested callbacks.

Code: Select all

Chain(function (continue)
    print 'fading in'
    Timer.add(1, continue)
end)(function (continue)
    print 'showing splash screen'
    Timer.add(1, continue)
end)(function (continue)
    print 'showing title screen'
    Timer.add(1, continue)
end)(function (continue)
    print 'playing demo'
end)()

Documentation and stuff forthcoming. Gist contains another example showing how callback arguments are handled. Looking for feedback; if you can think of a way to make this neater or think there are features missing let me know.

https://gist.github.com/airstruck/b610e10800e94adc980f

[Ulydev]

My text editor will thank you !

[airstruck]

My text editor will thank you !

That's exactly the kind of thing I had in mind. If you end up using Chain for that, I would love to see another screenshot.

[unek]

My text editor will thank you !

I didn't think this was possible outside node.js

[airstruck]

Have been playing with a coroutine-based alternative to Chain for flattening async code. No documentation yet, but here's a preview.

https://gist.github.com/airstruck/e4f11dc803848c158ca0

The wait function will return anything passed into the callback generated by continue. If continue is called more than once before a call to wait, only the first of those generated callbacks to be invoked will cause execution to continue.

[shakesoda]

The coroutine-based version is way, way better to write code for. This is awesome.

[farzher]

Not a bad idea node.js is my main language

Although I think next is the standard name for the callback function
continue usually means something else in programming languages
(also next is shorter)

[airstruck]

Not a bad idea node.js is my main language

Although I think next is the standard name for the callback function
continue usually means something else in programming languages
(also next is shorter)

I considered 'next' but it's a global in Lua. Of course you can name it whatever you like since it's just a parameter to a user defined function; neither solution here exposes any fixed identifiers. I sort of like "go" or "callback" too.

[farzher]

I considered 'next' but it's a global in Lua. Of course you can name it whatever you like since it's just a parameter to a user defined function; neither solution here exposes any fixed identifiers. I sort of like "go" or "callback" too.

I didn't realize `next` was a thing
While looking that up I also noticed lua has `goto`
They made some weird decisions on features. We don't get the basic continue, yet we get the dangerous goto
That's interesting though. Maybe I should refactor some loops to use `goto continue` instead of nesting if statements (slightly off topic, but we are talking about nesting)

[ejmr]

While looking that up I also noticed lua has `goto`. They made some weird decisions on features. We don't get the basic continue, yet we get the dangerous goto.

Personally I don't think that's weird or dangerous. Continue can be implemented in terms of goto. But the reverse isn't possible.