Coroutine.resume() inside Timer completion function

bowerandy

Is there a reason why it doesn't seem to be possible to resume a coroutine from within a Timer completion function? I have started to use coroutines much more often now for chaining animation sequences. They're significantly more convenient and flexible to use than just adding onComplete handlers to GTweens.

Try this:

local function printHelloAndYieldFor2() print("Hello") Timer.delayedCall(2000, function() coroutine.resume(coFunc) end) coroutine.yield() end   coFunc=coroutine.create( function() for i=1, 6 do printHelloAndYieldFor2() end end)   coroutine.resume(coFunc)

I would expect to see "Hello" printed out 6 times, once every 2 seconds.

best regards

atilim

Hi Andy,

If you change the line

Timer.delayedCall(2000, function() coroutine.resume(coFunc) end)

with

Timer.delayedCall(2000, function() print(coroutine.resume(coFunc)) end)

you can see the error which is "cannot resume running coroutine".

As you know resume runs in protected mode. Therefore, if there is any error inside a coroutine, Lua will not show the error message, but instead will return it to the resume call.

The solution is resuming the your coroutine inside another coroutine

Once I wrote a simple wait function with Timer.delayedCall and coroutines, hope it helps:

local function wait(delay) local co = coroutine.running() local co2 = coroutine.create(function() Timer.delayedCall(delay, function() coroutine.resume(co) end) end) coroutine.resume(co2) coroutine.yield() end   local function foo() print("foo 1") wait(1000) print("foo 2") wait(1000) print("foo 3") end   local co = coroutine.create(foo) coroutine.resume(co)

atilim

Also that wait function can be shortened a little bit with coroutine.wrap function:

local function wait(delay) local co = coroutine.running() coroutine.wrap(function() Timer.delayedCall(delay, function() coroutine.resume(co) end) end)() coroutine.yield() end

bowerandy

@atilim, wow, thanks for that. The wrap() method seems like it should solve it but I doubt I could have worked that out for myself!

I guess that ENTER_FRAME events are handled on another (coroutine) thread then, because resuming inside an ENTER_FRAME handler does seems to work okay.

best regards

atilim

I remember I had spent a couple of hours to write a correct wait() function.

I guess that ENTER_FRAME events are handled on another (coroutine) thread then, because resuming inside an ENTER_FRAME handler does seems to work okay.

Interesting. ENTER_FRAME and timer events are handled same. I cannot guess why ENTER_FRAME handler seems to work okay. (Maybe ENTER_FRAME doesn't work also ) (as a side note, I don't create or run any coroutines inside Gideros runtime. All function calls are handled by call() or pcall()).

bowerandy

@atilim, interesting.

This is what I've been doing to work around the problem. Do you remember that postToUpdateQueue() function I mentioned some time ago. Well, I implemented it using a dummy GTween with a completion function. IIRC, GTween uses ENTER_FRAME events to dispatch its completion functions.

function EventDispatcher:postToUpdateQueue(func) GTween.new(self, 0.001, {}, {onComplete=func}) end   local function safeResume(coFunc) stage:postToUpdateQueue(function() coroutine.resume(coFunc) end) end

Using safeResume() appears to work for me but only when the coroutine() is originallyy kicked off inside some form of callback like a touch handler. I think your coroutine.wrap() solution is neater so I'll try that instead.

best regards

bowerandy

@atilim, I'm getting a crash while using your wait() solution (and it also occurs with my postToUpdateQueue solution too). The crash appears to occur some time after having used any Timer within a coroutine. It seems to be in the C++ destructor for Timers so I'm guessing it might be a GC issue.

I'm having difficulty isolating a simple test case but if it helps, here is my wait code and a stack trace in Xcode after the crash.

function coroutine.wait(delay) local coFunc = coroutine.running() local co=coroutine.create(function() Timer.delayedCall(delay*1000, function() coroutine.resume(coFunc) end) end) coroutine.resume(co) -- postToUpdateQueue(function() Timer.delayedCall(delay*1000, function() coroutine.resume(coFunc) end) end) coroutine.yield() end

best regards

atilim

@bowerandy thanks for the bug report. I'll look into it.