Lua 5.2：更新系统（需要帮助）答案

【问题标题】：Lua 5.2: Update System (Need Help)Lua 5.2：更新系统（需要帮助）
【发布时间】：2014-10-27 21:11:49
【问题描述】：

我需要有关 Lua 文件编辑的帮助，因为我只是了解如何使用它...

这是我的代码：

local clientFile, serverFile = io.open("client.txt", "r"), io.open("server.txt", "r")

local clientVer, serverVer = tostring(clientFile:read()), tostring(serverFile:read())

io.write("\nCurrent Version: "..clientVer.."\nLast Version: "..serverVer.."\n\n")

if clientVer == serverVer then
    io.write("No Updates for now.\n\n")
elseif clientVer ~= serverVer then
    io.write("Updating...\n\n")
    os.remove("client.txt")
    local clientFileW = io.open("client.txt", "w+")
    clientFileW:write(serverVer)
    local clientFileR = io.open("client.txt", "r")
    io.write("Client Updated!\n\n")
    io.write("Current Version: "..tostring(clientFileR:read()).."\nLast Version: "..serverVer.."\n\n")
end

当我在客户端-服务器中具有相同版本时，这是我的输出：

Current Version: v2
Last Version: v2

No Updates for now.

这是我遇到敌人时的输出示例客户端：v1 和服务器：v8

Current Version: v1
Last Version: v8

Updating...

Client Updated!

Current Version: nil
Last Version: v8

为什么我有那个零？？？

【问题讨论】：

标签： io lua

【解决方案1】：

这里的问题是输出正在被缓冲（即没有立即写入文件）。此缓冲由C library functions which Lua uses for IO 完成。以下是您的代码中发生的事情的演练：

    -- ...
    -- new, empty file is created
    local clientFileW = io.open("client.txt", "w+")
    -- server version is stored in an internal buffer, waiting to be written to
    -- the file
    clientFileW:write(serverVer)
    local clientFileR = io.open("client.txt", "r")
    -- the empty client.txt is opened
    io.write("Client Updated!\n\n")
    -- since the client.txt file is empty, nil is returned by clientFileR:read()
    io.write("Current Version: "..tostring(clientFileR:read())
             .."\nLast Version: "..serverVer.."\n\n")
end
-- end of program execution, flush buffers (e.g. write the new version),
-- close files, etc.

为了解决您的程序，您可以在编写新的客户端版本后添加对:flush() 的调用。这将强制在该点将内部缓冲区写入文件：

-- ...
local clientFileW = io.open("client.txt", "w+")
clientFileW:write(serverVer)
clientFileW:flush()
local clientFileR = io.open("client.txt", "r")
-- ...

【讨论】：