CODEWITHSUNDEEP
lua
Max Power
Max Power

Reputation: 83

Lua global table with local link erasing

I have a module consisting of several files in which a global table is declared for passing messages between functions. When I try to clean up a global table a file other than main I get a collision, as far as I understand, this is due to the fact that I am making a link local values = _G.values; But I do it to improve performance when accessing this variable How do I clear the global(with using local link) table in another file? Perhaps there are other ways to transfer shared data between module files, without using accessing to _G

module:

main.lua
utils/a.lua
utils/b.lua

main.lua

os.setlocale("C")
package.path   = package.path .. ";./utils/?.lua";  -- luacheck: ignore
local Timer = require("timer")

_G.run = true;
_G.values = {};

local counter = 0;
local values = _G.values;
local timer_main = Timer:new()
timer_main:setInterval(1)

local timer_work = Timer:new()
timer_work:setInterval(10)


local a = require("utils.a");
local b = require("utils.b");

local function UpdateTable()
    counter = counter + 1
    print("Update table from main:       "..tostring(values))
    values[counter] = {Apple=counter+1, Banana=counter+2, Orange=counter+3}
end;


local function main()
    print("Global_main_start:            "..tostring(_G.values))
    print("Local_main_start:             "..tostring(values))
    while _G.run do
        if timer_main:isTimeout() then
            UpdateTable()
            print("Global_main_loop:             "..tostring(_G.values))
            print("Local_main_loop:              "..tostring(values))
            timer_main:setInterval(1)
        end
        b.TaskExecute()
        if timer_work:isTimeout() then
            _G.run = false
        end
    end
    print("Global_main_stop:             "..tostring(_G.values))
    print("Local_main_stop:              "..tostring(values))
end;


main()

a.lua

local Timer = require("timer")

local values = _G.values;
print("Local_after_require_a:        "..tostring(values))


local function EraseData()
    print("Global EraseData a before:    "..tostring(_G.values))
    print("Local EraseData a before:     "..tostring(values))
    _G.values = {}
    print("Global EraseData a after:     "..tostring(_G.values))
    print("Local EraseData a after:      "..tostring(values))
end;

return {
    EraseData = EraseData
}

b.lua

local Timer = require("timer")

local values = _G.values;
local a = a or require("a");
local timer_b = Timer:new()
timer_b:setInterval(3)
print("Local_after_require_b:        "..tostring(values))

local function TaskExecute()
    if timer_b:isTimeout() then
        print("Global Execute b before:      "..tostring(_G.values))
        print("Local Execute b before:       "..tostring(values))
        if #values > 0 then
            for i = 1, #values do
                print("         Values item: "..i.."       "..tostring(values[i]))
            end
        end
        a.EraseData()
        print("Global Execute b after:       "..tostring(_G.values))
        print("Local Execute b after:        "..tostring(values))
        timer_b:setInterval(3)
    end
end;

return {
    TaskExecute = TaskExecute
}

timer.lua (just for execute func at same time)

local base   = _G;
local math   = math;
local os     = os;

local Timer = {}


local function new(self)
    local timer = {
        deadline = os.time()
    }
    base.setmetatable(timer, self)
    self.__index = self
    return timer
end

Timer.new = new

local function setInterval(self, duration)
    self.deadline = os.time() + duration
end

Timer.setInterval = setInterval

local function setDate(self, date)
    self.deadline = os.time(date)
end

Timer.setDate = setDate

local function getSecondsLeft(self)
    return math.max(0, self.deadline - os.time())
end

Timer.getSecondsLeft = getSecondsLeft


local function isTimeout(self)
    return os.time() >= self.deadline
end

Timer.isTimeout = isTimeout

return Timer

Output:

Local_after_require_a:        table: 0x7ff50ac09230
Local_after_require_a:        table: 0x7ff50ac09230
Local_after_require_b:        table: 0x7ff50ac09230
Global_main_start:            table: 0x7ff50ac09230
Local_main_start:             table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50ac09230
Local_main_loop:              table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50ac09230
Local_main_loop:              table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50ac09230
Local_main_loop:              table: 0x7ff50ac09230
Global Execute b before:      table: 0x7ff50ac09230
Local Execute b before:       table: 0x7ff50ac09230
         Values item: 1       table: 0x7ff50ac07be0
         Values item: 2       table: 0x7ff50c0040d0
         Values item: 3       table: 0x7ff50af049d0
Global EraseData a before:    table: 0x7ff50ac09230
Local EraseData a before:     table: 0x7ff50ac09230
Global EraseData a after:     table: 0x7ff50af05510   <--- Erased Global var in a.lua 
Local EraseData a after:      table: 0x7ff50ac09230   <--- Local var in a.lua not changed 
Global Execute b after:       table: 0x7ff50af05510   <--- Global var in b.lua changed 
Local Execute b after:        table: 0x7ff50ac09230   <--- Local var in b.lua not changed 
Update table from main:       table: 0x7ff50ac09230   <--- Add new values in old local var in main.lua
Global_main_loop:             table: 0x7ff50af05510  <--- Global var in main.lua changed 
Local_main_loop:              table: 0x7ff50ac09230  <--- Local var in main.lua not changed
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50af05510
Local_main_loop:              table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50af05510
Local_main_loop:              table: 0x7ff50ac09230
Global Execute b before:      table: 0x7ff50af05510
Local Execute b before:       table: 0x7ff50ac09230
         Values item: 1       table: 0x7ff50ac07be0
         Values item: 2       table: 0x7ff50c0040d0
         Values item: 3       table: 0x7ff50af049d0
         Values item: 4       table: 0x7ff50c004280
         Values item: 5       table: 0x7ff50ac08bb0
         Values item: 6       table: 0x7ff50c004410
Global EraseData a before:    table: 0x7ff50af05510
Local EraseData a before:     table: 0x7ff50ac09230
Global EraseData a after:     table: 0x7ff50c004940
Local EraseData a after:      table: 0x7ff50ac09230
Global Execute b after:       table: 0x7ff50c004940
Local Execute b after:        table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50c004940
Local_main_loop:              table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50c004940
Local_main_loop:              table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50c004940
Local_main_loop:              table: 0x7ff50ac09230
Global Execute b before:      table: 0x7ff50c004940
Local Execute b before:       table: 0x7ff50ac09230
         Values item: 1       table: 0x7ff50ac07be0
         Values item: 2       table: 0x7ff50c0040d0
         Values item: 3       table: 0x7ff50af049d0
         Values item: 4       table: 0x7ff50c004280
         Values item: 5       table: 0x7ff50ac08bb0
         Values item: 6       table: 0x7ff50c004410
         Values item: 7       table: 0x7ff50ac09380
         Values item: 8       table: 0x7ff50ac09510
         Values item: 9       table: 0x7ff50c004350
Global EraseData a before:    table: 0x7ff50c004940
Local EraseData a before:     table: 0x7ff50ac09230
Global EraseData a after:     table: 0x7ff50c004b90
Local EraseData a after:      table: 0x7ff50ac09230
Global Execute b after:       table: 0x7ff50c004b90
Local Execute b after:        table: 0x7ff50ac09230
Update table from main:       table: 0x7ff50ac09230
Global_main_loop:             table: 0x7ff50c004b90
Local_main_loop:              table: 0x7ff50ac09230
Global_main_stop:             table: 0x7ff50c004b90
Local_main_stop:              table: 0x7ff50ac09230

Upvotes: 2

Views: 120

Answers (1)

Nifim
Nifim

Reputation: 5031

Doing _G.values = {} does not "erase" the table. it only changes the reference of _G.values to a newly created table. the previous table _G.values pointed to is completely unchanged and any other references(such as a's local values) will remain unchanged. you can see this by the value shown in your print statements.

table: 0x7ff50ac09230 this is the original table

table: 0x7ff50af05510 this is the new table

because you are not altering table: 0x7ff50ac09230 you will not see any change to a's local values.

I suggest you push the table value you want to clear down a level so that it is inside the table you're referencing:

main

messages = {}
messages.values = {}

a

local messages = _G.messages
...

messages.values = {}

I also find it unnecessary to use _G in the code you provided, just do local values = values the right values would be the global, if you needed to access the "original" value now that it is shaded by the local then _G would make sense.

Upvotes: 1

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