A Threads class with coroutine

Introduction

Problem description

When I tried to run some functions like terrain generating. Because it need a long time to finish, so I have to face a black screen without any information appear. This is because of the mechanism of Codea:

when setup() is running, the draw() won't run, when setup() is finished, it will run the draw(). But these functions must run once, so they need to be put into setup().

When I use these functions in setup() and I want to see some information drawing on the screen, how can I do?

I found coroutine can deal with this problem, then I began to learn it.

Solution

I am learning and writing a Threads class. Using it we can solve the problem.

Threads class

Class code

The class code

--# ThreadsThreads = class()function Threads:init()    self.threads = {}        self.taskList = {}    self.time = os.clock()       self.timeTick = 0.01    self.taskID = 1    self.taskStatus = {}    self.taskVT = {}    self.img = image(100,100)end-- Add task function into the task listfunction Threads:addTaskToList(task)    local t = function() task() end    table.insert(self.taskList, t)end-- Create coroutine for all task, run oncefunction Threads:job()        local n = #self.taskList    for id = 1, n do        -- local f = function () self.taskList[id]() end        local f = function () self:taskUnit(id) end        local co = coroutine.create(f)        table.insert(self.threads, co)           -- Record all tasks' status,  now should be suspended        self.taskStatus[id] = coroutine.status(co)    endend-- Task unitfunction Threads:taskUnit(id)    self.taskID = id    self.taskList[id]()    -- self:switchPoint(id)          -- self.taskStatus[id] = "Finished" end-- Switch point, put this function into the task functionfunction Threads:switchPoint(id)    -- Switch task，when its timetick is used and task have not finished    if (os.clock() - self.time) >= self.timeTick then           -- Debug info, do not put the print into the task function        print("hello: No."..id.." is "..self.taskStatus[id])          -- self:visual(id)        -- reset task time        self.time = os.clock()          -- Pause the task         coroutine.yield()        endend-- Put this function into draw()function Threads:dispatch()    local n = #self.threads    if n == 0 then return end       for i = 1, n do		-- Record the current task		self.taskID = i    		local status = coroutine.resume(self.threads[i])		-- Record all the tasks' status		self.taskStatus[i] = coroutine.status(self.threads[i])		-- If task finished, then remove it from self.threads, and return		if not status then            self.taskStatus[i] = "Finished"             table.remove(self.threads, i)            -- table.remove(self.taskList,i)            return        end    endend --[[function Threads:visual(id)    local n = #self.taskList    local vt = {}    background(18, 16, 16, 255)    setContext(self.img)    pushStyle()    strokeWidth(1)    fill(255, 211, 0, 255)    -- if self.taskID == 1 then fill(241, 7, 7, 255) else fill(255, 211, 0, 255) end    local w,h = self.img.width/n, self.img.height/n    local x,y = 0,0    for i = 1, n do        vt[i] = function () rect(100+x+(i-1)*w,100+y+(i-1)*h,w,h) end    end        popStyle()    setContext()    -- sprite(self.img,300,300)    -- vt[self.taskID]()    print("id: "..id)    vt[id]()end--]]```	The test code:

--# Main function setup() print("Thread testing ...")

myT = Threads()myT.timeTick = 1/60myT:addTaskToList(tt)myT:addTaskToList(oo)myT:addTaskToList(mf)myT:addTaskToList(pk)--[[ myT.taskList[2]()--]]myT:job()print(unpack(myT.taskList))

end

function draw() background(0)

myT:dispatch()fill(244, 27, 27, 255)print("2: "..myT.taskStatus[1])print("length: "..#myT.taskList)sysInfo()

end

-- The task functions

function tt () while true do -- print("tt: "..os.clock()) myT:switchPoint(myT.taskID) end end

function oo () while true do -- print("oo: "..os.clock()) myT:switchPoint(myT.taskID) end end

function mf () local k = 0 for i=1,10000000 do k = k + i -- print("mf: "..k) -- If the time >= timeTick then pause myT:switchPoint(myT.taskID) end end

function pk () local k = 0 for i=1,10000000 do k = k + i -- print("pk: "..k) -- If the time >= timeTick then pause myT:switchPoint(myT.taskID) end end

###	UsageAssume we have a function `createTerrain()` to generate the terrain in `setup()`, and it will take a long time, we can do like below:

function setup()

myT = Threads()myT.timeTick = 1/60myT:addTaskToList(createTerrain)myT:job()

end

function draw() background(0)

myT:dispatch()drawLoadingScreen()

end

-- This is the loading screen function drawLoadingScreen() ... -- Show some information text("Creating the terrain, please wait...") ... end

-- The function will run for a long time function createTerrain() ... for i=1,10000 do for j= 1, 100000 do ... -- Put the switchPoint() here myT:switchPoint(myT.taskID) end end ...

for i=1,200000 do	for j= 1, 300000 do		...		-- Put the switchPoint() here		myT:switchPoint(myT.taskID)	endend...

end

If the function is a method of a class, like `Map:createTerrain()`, we can load it like below:

myT:addTaskToList(function () Map:createTerrain() end)

OK, it is all.BTW. This is for the newbie, if you are experienced, please ignore it. :)