把所有的值连接起来，然后追加到同一个变量中。

2013-1-17 16:35:12
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我试图将所有值连接起来并将其附加到同一个变量中，然后写入字符串的内容。我一直得到错误:“尝试连接全局'arglist'(一个无值)”

  eo_device = {}

  eo_device[1] = {node = "ME", t_object = "AV1", h_object = "AV2" }
  eo_device[2] = {node = "ME", t_object = "AV3", h_object = "AV4" }
  eo_device[3] = {node = "ME", t_object = "AV5", h_object = "AV6" }
  eo_device[4] = {node = "ME", t_object = "AV7", h_object = "AV8" }
  eo_device[5] = {node = "ME", t_object = "AV9", h_object = "AV10" }
  eo_device[6] = {node = "ME", t_object = "AV11", h_object = "AV12" }
  eo_device[7] = {node = "ME", t_object = "AV13", h_object = "AV14" }
  eo_device[8] = {node = "ME", t_object = "AV15", h_object = "AV16" }
  eo_device[9] = {node = "ME", t_object = "AV17", h_object = "AV18" }
  eo_device[10] = {node = "ME", t_object = "AV19", h_object = "AV20" }
  eo_device[11] = {node = "ME", t_object = "AV21", h_object = "AV22" }
  eo_device[12] = {node = "ME", t_object = "AV23", h_object = "AV24" }
  eo_device[13] = {node = "ME", t_object = "AV25", h_object = "AV26" }
  eo_device[14] = {node = "ME", t_object = "AV27", h_object = "AV28" }
  eo_device[15] = {node = "ME", t_object = "AV29", h_object = "AV30" }

--生成一个包含所有要写入CSV中的参数的字符串
for deviceindex = 1,#eo_device do

 device_name = scl.nodes[eo_device[deviceindex].node][eo_device[deviceindex].t_object .. "_Object_Name"].value -- 指向对象名称
 description = scl.nodes[eo_device[deviceindex].node][eo_device[deviceindex].t_object .. "_Description"].value --指向所有对象的描述
 temperature = scl.nodes[eo_device[deviceindex].node][eo_device[deviceindex].t_object .. "_Present_Value"].value --温度对象的值
 humidity = scl.nodes[eo_device[deviceindex].node][eo_device[deviceindex].h_object .. "_Present_Value"].value --湿度对象的值

 buflist = device_name .. "," .. description .. "," .. temperature .. "," .. humidity

 arglist = arglist .. "," .. buflist

 end -- 结束

--然后退出循环:
arglist = arglist .. "," .. buflist

buffer = os.date() .. arglist .. "\r\n"

file, info = io.open("trend.csv", "a+") -- 写入CSV
if file then
file:write(buffer)
file:close()
end -- 结束
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用户501459
用户501459

我一直在得到错误消息："尝试连接全局变量'arglist'（一个nil值）"，因为您正在尝试在代码的第31行连接arglist（一个nil值）：

arglist = arglist .. "," .. buflist

arglist从未初始化，因此在=号右侧尝试进行连接时，会出现此错误。

关于此循环的侧注：

for deviceindex = 1,#eo_device do

    description = scl.nodes[eo_device[deviceindex].node][eo_device[deviceindex].t_object .. "_Description"].value

Lua有一个“通用”的for循环，允许您迭代所有eo_device的元素，为您提供索引和值，因此您不必在循环内部进行索引。这将使您的代码更加简洁：

for deviceindex, device in ipairs(eo_device) do

    description = scl.nodes[device.node][device.t_object .. "_Description"].value

关于此代码的侧注：

buflist = device_name .. "," .. description .. "," .. temperature .. "," .. humidity

如此构建字符串效率极低。在循环中执行此操作会导致成千上万个字符串连接并生成大量垃圾。更好的方法是将所有字符串部分添加到表中，然后通过table.concat将它们连接成单个逗号分隔的字符串。

例如，要创建一个包含eo_device表中所有字符串的逗号分隔字符串：

local buffer = {}

for i，device in ipairs(eo_device) do
    table.insert(buffer，device.node)
    table.insert(buffer，device.t_object)
    table.insert(buffer，device.h_object)
end

devices = table.concat(buffer, ',')
2013-01-17 17:14:23

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用户1678633

用户1678633
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