Lua - 连接传递给函数的几个参数，直到满足条件，然后将字符串传递给下一个函数

Question

pvMessage 是从另一个函数发送的，消息通常几乎立即分几部分出现。我正在寻找存储 pvMessages 并将消息连接到最后。因此创建了一个包含所有部分的主字符串。

Example.
pvMessage #1 = thisispart1msg
pvMessage #2 = now part two is being received
pvMessage #3 = Part 3

MasterMessage = thisispart1msgnow part two is being receivedPart 3

我已尝试多次尝试解决此问题。事实证明，在函数之外存储消息比我更难，但我一直在覆盖之前的消息。

    function ProcessClientMessage( pvMessage ) 
         if StartMessage == "" then
            StartMessage = pvMessage                
            pvMessage = ""
         end

         if pvMessage ~= "" then
             if MiddleMessage == "" then
                MiddleMessage = pvMessage
                pvMessage = StartMessage .. MiddleMessage
                pvMessage = ""
             end
          end

         if pvMessage ~= "" then
            if EndMessage == "" then
                EndMessage = pvMessage
                pvMessage = StartMessage .. MiddleMessage .. EndMessage
                pvMessage = ""
             end
         end

         if pvMessage ~= "" then
            ProcessClientMessageReset()
         end 
    end

Answer 1

您可以使用“或”赋值来简化全局变量的初始化，然后将字符串连接到结果。考虑：

function ProcessClientMessage(msg)
    msg_global_ = (msg_global_ or "")..msg
    print(msg_global_) -- Just for debug purposes so we can print each step
end

do
    ProcessClientMessage("thisispart1msg")
    ProcessClientMessage("now part two is being received")
    ProcessClientMessage("Part 3")
end

变量msg_global_ 包含正在构建的字符串。如果它还没有被添加，那么它将是 nil。在这种情况下，or "" 将被执行并且默认字符串为空。

然后我们只需附加字符串msg。

输出如下：

thisispart1msg
thisispart1msgnow part two is being received
thisispart1msgnow part two is being receivedPart 3

当您实际处理消息时，只需将全局变量设置为 nil 即可。

Answer 2

这个问题也可以用协程解决：

local function consumer(consume)
   print(consume()..consume()..consume())
   return consumer(consume)
end

local process = coroutine.wrap(consumer)
process(coroutine.yield)

process('foo')
process('bar')
process('baz')

process('hello')
process('world')
process('test')

---

编辑：正如 Egor 所指出的，评估的顺序在技术上没有定义（尽管在我知道的每个 Lua 实现中它都是从左到右的）所以即使你的解释器正在做@987654322，这里有一个替代方案也可以工作@-like 优化：

local function consumer(consume)
   local a = consume()
   local b = consume()
   local c = consume()
   print(a .. b .. c)
   return consumer(consume)
end

Answer 3

如果您总是要连接三个部分，则可能会这样：

local buffer = {}
local function ProcessClientMessage(pvMessage) 
  if #buffer < 3 then
    table.insert(buffer, pvMessage)
  else
    --ProcessClientMessageReset(table.concat(buffer, ""))
    print(table.concat(buffer, ""))
    buffer = {}
  end
end
ProcessClientMessage("thisispart1msg")
ProcessClientMessage("now part two is being received")
ProcessClientMessage("Part 3")

ProcessClientMessage("more thisispart1msg")
ProcessClientMessage("some now part two is being received")
ProcessClientMessage("Part 4")

这应该打印出来：

thisispart1msgnow part two is being receivedPart 3
more thisispart1msgsome now part two is being receivedPart 4