Function Dump/Coroutine Manipulation

< Function Dump

Up one category:
Main Page

Control of coroutines can be done through functions within the coroutine table. Take a look at the See Also section for discussion on what a coroutine is and how they are used.

coroutine.create(f)

Creates a new coroutine, with body f. f must be a Lua function. Returns this new coroutine, an object with type "thread". This thread object cannot be called like a normal function can be.

function Test ()
print"Hello World!"
end
local coro = coroutine.create(Test)
print(type(coro))
coro()

thread

Error: attempt to call local 'coro' (a thread value)

coroutine.resume(co [, val1, ···])

Starts or continues the execution of coroutine co. The first time you resume a coroutine, it starts running its body. The values val1, ··· are passed as the arguments to the body function. If the coroutine has yielded, resume restarts it; the values val1, ··· are passed as the results from the yield.

If the coroutine runs without any errors, resume returns true plus any values passed to yield (if the coroutine yields) or any values returned by the body function (if the coroutine terminates). If there is any error, resume returns false plus the error message.

function f(a, b, c)
    print(a, b, c)
end

thread = coroutine.create(f) 
coroutine.resume(thread, 1, 2, 3)

1 2 3

NOTE: The Roblox wait() function internally calls coroutine.yield() so this function will return at that point. The wait() will automatically call coroutine.resume() again when the wait time completes.

coroutine.running()

Returns the running coroutine, or nil when called by the main thread.

co = coroutine.create(function() 
    print(coroutine.running() == co)
end)

coroutine.resume(co)

true

coroutine.status(co)

Returns the status of coroutine co, as a string: "running", if the coroutine is running (that is, it called status); "suspended", if the coroutine is suspended in a call to yield, or if it has not started running yet; "normal" if the coroutine is active but not running (that is, it has resumed another coroutine); and "dead" if the coroutine has finished its body function, or if it has stopped with an error.

function f(a, b, c)
    print(a, b, c)
end

thread = coroutine.create(f) 
coroutine.resume(thread, 1, 2, 3)
print(coroutine.status(thread))

1 2 3

dead

coroutine.wrap(f)

Creates a new coroutine, with body f. f must be a Lua function. Returns a function that resumes the coroutine each time it is called. Any arguments passed to the function behave as the extra arguments to resume. Returns the same values returned by resume, except the first boolean. In case of error, propagates the error.

function f(s)
  print("Entering f with value", s)
  v = coroutine.yield()
  print("After yield, v is", v)
  return 22
end

resumer = coroutine.wrap(f) 
resumer(88)
resumer(99)

Entering f with value 88

After yield, v is 99

coroutine.yield (···)

Suspends the execution of the calling coroutine. The coroutine cannot be running a C function, a metamethod, or an iterator. Any arguments to yield are passed as extra results to resume.

co = coroutine.create(function()
    print(coroutine.yield())
end)
coroutine.resume(co)
coroutine.resume(co, 4, 5)

4 5

See Also

• Beginners Guide to Coroutines
• Programming in Lua: Coroutine Basics
• Coroutine Tutorial