带有本地链接擦除的 Lua 全局表答案

【问题标题】：Lua global table with local link erasing带有本地链接擦除的 Lua 全局表
【发布时间】：2020-12-21 14:21:45
【问题描述】：

我有一个由多个文件组成的模块，其中声明了一个全局表，用于在函数之间传递消息。当我尝试清理除 main 以外的全局表时，我遇到了冲突，据我所知，这是因为我正在创建一个链接 local values = _G.values; 但我这样做是为了提高访问此变量时的性能如何清除另一个文件中的全局（使用本地链接）表？也许还有其他方法可以在模块文件之间传输共享数据，而不使用访问_G

模块：

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（仅用于同时执行函数）

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

输出：

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

【问题讨论】：

您可以通过删除所有元素来清理表格：for k in pairs(values) do values[k]=nil end

标签： lua

【解决方案1】：

执行_G.values = {} 不会“擦除”表格。它只会将_G.values 的引用更改为新创建的表。先前指向的表_G.values 完全不变，任何其他引用（例如a 的本地values）将保持不变。您可以通过打印语句中显示的值看到这一点。

table: 0x7ff50ac09230这是原表

table: 0x7ff50af05510这是新表

因为您没有更改table: 0x7ff50ac09230，所以您不会看到a 的本地values 有任何变化。

我建议您将要清除的表值下推一个级别，以便它在您引用的表内：

主要

messages = {}
messages.values = {}

一个

local messages = _G.messages
...

messages.values = {}

我还发现没有必要在您提供的代码中使用_G，只需执行local values = values 正确的值将是全局的，如果您现在需要访问“原始”值，因为它被本地遮蔽了那么_G 就有意义了。

【讨论】：