table 调用函数时返回 nil 值

Question

我试图通过几个函数传递 table 并 return 它，但它只在一定程度上起作用。我几乎可以肯定它必须与范围界定有关，但我无法解决这个问题，因为我是 LUA 的新手。我尝试将 table 放在第 1 行并将其设置为全局，但无济于事。错误：包参数：预期 table 但没有得到。

function returnToTunnel(movementTable)
    for i = table.maxn(movementTable), 1, -1  do  --this is where I get the error.
        if (movementTable[i] == 1) then
            turtle.down()
        elseif (movementTable[i] == 2) then
            turtle.up()
        elseif (movementTable[i] == 3) then
            turtle.back()
            turtle.turnRight()
        elseif (movementTable[i] == 4) then
            turtle.back()
            turtle.turnLeft()
        elseif (movementTable[i] == 5) then
            turtle.back()
        end
    end
end

function mineOre(locationParam, movementTable)
    if (locationParam == 1) then
        turtle.digUp()
        turtle.suckUp()
        turtle.up()
        table.insert(movementTable, 1)
    elseif (locationParam == 2) then
        turtle.digDown()
        turtle.suckDown()
        turtle.down()
        table.insert(movementTable, 2)
    elseif (locationParam == 3) then
        turtle.turnLeft()
        turtle.dig()
        turtle.suck()
        turtle.forward()
        table.insert(movementTable, 3)
    elseif (locationParam == 4) then
        turtle.turnRight()
        turtle.dig()
        turtle.suck()
        turtle.forward()
        table.insert(movementTable, 4)
    elseif (locationParam == 5) then
        turtle.dig()
        turtle.suck()
        turtle.forward()
        table.insert(movementTable, 5)
    end
    locationParam = oreCheck()
    if (locationParam > 0) then
        mineOre(locationParam, movementTable)
    else
        return movementTable
    end
end

function digTunnel(tunnelLengthParam)
    local oreFound
    local movement = {}

    for i = 1, tunnelLengthParam do
        turtle.dig()
        turtle.forward()
        oreFound = oreCheck()
        if (oreFound > 0) then
            movement = mineOre(oreFound, movement)
            returnToTunnel(movement)
        end
        if ((i % 2) == 1) then
            turtle.digUp()
            turtle.up()
        elseif ((i % 2) == 0) then
            turtle.digDown()
            turtle.down()
        end
        oreFound = oreCheck()
        if (oreFound > 0) then
            movement = mineOre(oreFound, movement)
            returnToTunnel(movement)
        end
    end
end

因此，digTunnel 函数调用了另外两个函数 mineOre 和 returnToTunnel。

我一直在查看 LUA 手册和几个网站，但无法弄明白。感谢您的帮助！

Answer 1

当 locationParam > 0 时，您的函数 mineOre 不是 return table 而是 nil。

if (locationParam > 0) then
  mineOre(locationParam, movementTable)
else
  return movementTable
end

因此这将导致 nil 值最终出现在 table.maxn

 movement = mineOre(oreFound, movement)
 returnToTunnel(movement)

table 调用函数时返回 nil 值

table returning nil value when calling function

lua

function

parameter-passing

lua-table