การสร้างโคโรทีน

Coroutine คืออะไร

local co = coroutine.create(function()
  print("start")
  coroutine.yield()
  print("resumed")
  coroutine.yield()
  print("done")
end)

print(coroutine.status(co))   -- suspended
coroutine.resume(co)          -- start
print(coroutine.status(co))   -- suspended
coroutine.resume(co)          -- resumed

coroutine.create เทียบกับ coroutine.wrap

-- create: returns coroutine object
local co = coroutine.create(function(x)
  return x * 2
end)
local ok, val = coroutine.resume(co, 5)
print(ok, val)   -- true  10

-- wrap: returns a resumable function
local gen = coroutine.wrap(function(x)
  return x * 3
end)
print(gen(5))    -- 15

วงจรชีวิตของ Coroutine

local co = coroutine.create(function()
  coroutine.yield()
end)

print(coroutine.status(co))  -- suspended
coroutine.resume(co)          -- runs until yield
print(coroutine.status(co))  -- suspended again
coroutine.resume(co)          -- runs until end
print(coroutine.status(co))  -- dead

การเรียกใช้ Coroutine หลายตัว

local function worker(name, steps)
  for i = 1, steps do
    print(name .. ": step " .. i)
    coroutine.yield()
  end
end

local co1 = coroutine.create(function() worker("A", 3) end)
local co2 = coroutine.create(function() worker("B", 3) end)

for _ = 1, 3 do
  coroutine.resume(co1)
  coroutine.resume(co2)
end
-- A:1, B:1, A:2, B:2, A:3, B:3

การวนซ้ำด้วย coroutine.wrap

local function range(n)
  return coroutine.wrap(function()
    for i = 1, n do
      coroutine.yield(i)
    end
  end)
end

for v in range(5) do
  io.write(v .. " ")
end
print()  -- 1 2 3 4 5

ข้อผิดพลาดใน Coroutine

local co = coroutine.create(function(x)
  if x < 0 then error("negative input: " .. x) end
  return math.sqrt(x)
end)

local ok, val = coroutine.resume(co, -1)
print(ok, val)    -- false  input:2: negative input: -1
print(coroutine.status(co))  -- dead

-- Can't resume a dead coroutine:
ok, val = coroutine.resume(co)
print(ok, val)    -- false  cannot resume dead coroutine

ข้อมูลประจำตัวของ Coroutine

local co = coroutine.create(function()
  local self, isMain = coroutine.running()
  print("type:", type(self))      -- thread
  print("isMain:", isMain)        -- false
  print("status:", coroutine.status(self)) -- running
end)

coroutine.resume(co)

-- In main thread:
local main, isMain = coroutine.running()
print("main isMain:", isMain)    -- true

ตัวสร้างแบบไม่สิ้นสุด

local function naturals(start)
  return coroutine.wrap(function()
    local n = start or 1
    while true do
      coroutine.yield(n)
      n = n + 1
    end
  end)
end

local gen = naturals(1)
for i = 1, 8 do
  io.write(gen() .. " ")
end
print()  -- 1 2 3 4 5 6 7 8

Coroutine ในฐานะงาน

local tasks = {}

local function spawn(fn)
  tasks[#tasks+1] = coroutine.create(fn)
end

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

spawn(function() for i=1,3 do print("T1:"..i); coroutine.yield() end end)
spawn(function() for i=1,3 do print("T2:"..i); coroutine.yield() end end)
run()

หน่วยความจำของโครูทีน

-- Coroutine pool concept
local pool = {}

local function getCoroutine(fn)
  -- Reuse dead coroutine slots
  for i, co in ipairs(pool) do
    if coroutine.status(co) == "dead" then
      pool[i] = coroutine.create(fn)
      return pool[i]
    end
  end
  local co = coroutine.create(fn)
  pool[#pool+1] = co
  return co
end

print("Pool pattern for coroutine reuse")

ตรวจสอบความเข้าใจอย่างรวดเร็ว

สรุป: การสร้างโครูทีน