สถานะโคโรทีน

สถานะของโครูทีนสี่สถานะ

local co = coroutine.create(function()
  print(coroutine.status(coroutine.running()))  -- running
  coroutine.yield()
end)

print(coroutine.status(co))  -- suspended
coroutine.resume(co)          -- prints: running
print(coroutine.status(co))  -- suspended
coroutine.resume(co)
print(coroutine.status(co))  -- dead

สถานะ “ปกติ”

local inner, outer

inner = coroutine.create(function()
  print("outer status:", coroutine.status(outer))  -- normal
  coroutine.yield()
end)

outer = coroutine.create(function()
  coroutine.resume(inner)
end)

coroutine.resume(outer)
-- prints: outer status: normal

ตรวจสอบก่อนดำเนินการต่อ

local function safeResume(co, ...)
  local status = coroutine.status(co)
  if status == "dead" then
    return false, "cannot resume dead coroutine"
  end
  if status == "running" then
    return false, "cannot resume running coroutine"
  end
  return coroutine.resume(co, ...)
end

สถานะหลังเกิดข้อผิดพลาด

local co = coroutine.create(function()
  error("something went wrong")
end)

local ok, err = coroutine.resume(co)
print(ok, err)                      -- false  ...: something went wrong
print(coroutine.status(co))         -- dead

-- Cannot resume dead coroutine:
local ok2, err2 = coroutine.resume(co)
print(ok2, err2)  -- false  cannot resume dead coroutine

coroutine.isyieldable

local co = coroutine.create(function()
  print("isyieldable:", coroutine.isyieldable())  -- true
  coroutine.yield()
end)

coroutine.resume(co)

-- In main thread:
print("isyieldable:", coroutine.isyieldable())  -- false
-- coroutine.yield()  -- ERROR in main thread

การตรวจสอบกลุ่มโครูทีน

local function makeWorker(n, name)
  return coroutine.create(function()
    for i = 1, n do
      print(name, "step", i)
      coroutine.yield()
    end
  end)
end

local workers = {
  makeWorker(2, "fast"),
  makeWorker(4, "slow"),
}

while #workers > 0 do
  local alive = {}
  for _, co in ipairs(workers) do
    coroutine.resume(co)
    if coroutine.status(co) ~= "dead" then
      alive[#alive+1] = co
    end
  end
  workers = alive
end

การแก้ไขข้อบกพร่องของโครูทีน

local function namedCo(name, fn)
  local co = coroutine.create(fn)
  return {
    co = co,
    name = name,
    resume = function(self, ...)
      print("[" .. self.name .. "] resume")
      local results = table.pack(coroutine.resume(self.co, ...))
      print("[" .. self.name .. "] status: " .. coroutine.status(self.co))
      return table.unpack(results, 1, results.n)
    end
  }
end

local worker = namedCo("worker1", function()
  coroutine.yield()
end)
worker:resume()
worker:resume()

การเริ่มโครูทีนที่สิ้นสุดแล้วใหม่

local function makeCounter(start, step)
  return coroutine.wrap(function()
    local n = start or 0
    while true do
      coroutine.yield(n)
      n = n + (step or 1)
    end
  end)
end

local count = makeCounter(0, 2)
for i = 1, 5 do io.write(count() .. " ") end
print()  -- 0 2 4 6 8

-- "Restart" by creating a new one
count = makeCounter(100)
print(count())   -- 100

พฤติกรรมข้อผิดพลาดของ Coroutine.wrap

local gen = coroutine.wrap(function()
  coroutine.yield(1)
  error("oops")
  coroutine.yield(2)  -- never reached
end)

print(gen())   -- 1 (ok)
local ok, err = pcall(gen)
print(ok, err) -- false  ...: oops
-- Subsequent call: dead coroutine
ok, err = pcall(gen)
print(ok, err) -- false  cannot resume dead coroutine

isyieldable เทียบกับ status

local function maybeYield()
  if coroutine.isyieldable() then
    coroutine.yield()
  else
    -- in main thread or non-yieldable context
    print("cannot yield here")
  end
end

maybeYield()  -- prints "cannot yield here" (main thread)

local co = coroutine.create(maybeYield)
coroutine.resume(co)   -- yields successfully

ตรวจสอบความเข้าใจอย่างรวดเร็ว

สรุป: สถานะของโครูทีน