Stone's Note
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Lua coroutine

发表于 更新于

API

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-- create function,It returns a value of type thread, which represents the new coroutine
co = coroutine.create(funtion
    print("hi")
end)

-- check the state of a coroutine
coroutine.status(co)

-- starts the execution of a coroutine
coroutine.resume(co)

-- The real power of coroutines stems from the yield function, which allows a running coroutine to suspend its execution so that it can be resumed later
coroutine.yield()

Status

  • suspend
  • running
  • normal
  • dead

Status Switching

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(create)
   |
   |
   v        caller resume the coroutime                 resume other coroutine
suspend  ------------------------------->  running --------------------------------> normal 
         <------------------------------      |     <-------------------------------
            yield                             |return   other coroutine yield/return
           (return controll to caller)        |
                                              v
                                             dead
                                   (return controll to caller)

note

Note that 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.

A useful facility in Lua is that a pair resume-yield can exchange data between them. The first resume, which has no corresponding yield waiting for it, passes its extra arguments as arguments to the coroutine main function

Example

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function status()
    print("co1's status :"..coroutine.status(co1).." ,co2's status: "..coroutine.status(co2))
end

co1 = coroutine.create(function ( a )
    print("arg is :"..a)
    status()

    local stat, rere = coroutine.resume(co2,"2")
    print("resume's return is "..rere)
    status()

    local stat2,rere2 = coroutine.resume(co2,"4")
    print("resume's return is "..rere2)

    local arg = coroutine.yield("6")
end)

co2 = coroutine.create(function ( a )
    print("arg is :"..a)
    status()

    local rey = coroutine.yield("3")
    print("yeild's return is " .. rey)
    status()

    coroutine.yield("5")
end)

stat,mainre = coroutine.resume(co1,"1")
status()
print("last return is "..mainre)

output

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arg  1
co1's status :running ,co2's status: suspended
arg is :2
co1's status :normal ,co2's status: running
resume's return is 3
co1's status :running ,co2's status: suspended
yeild's return is 4
co1's status :normal ,co2's status: running
resume's return is 5
co1's status :suspended ,co2's status: suspended
last return is 6

Reference & Thanks