[英]Lua - “attempt to compare number with nil” error
a={51,31,4,22,23,45,23,43,54,22,11,34}
colors={"white","white","white","white","white","white","white","white","white","white","white","white","white","white","white","white","white"}
function try(f, catch_f)
local status, exception = pcall(f)
if not status then
catch_f(exception)
end
end
function refreshColors(yellowEndIndex,redIndex,blueIndex)
for ccnt=1,table.getn(a),1 do
if ccnt < yellowEndIndex then
colors[ccnt] = "yellow"
elseif ccnt == redIndex then
colors[ccnt] = "red"
elseif ccnt == blueIndex then
colors[ccnt] = "blue"
else
colors[ccnt] = "white"
end
end
end
try(refreshColors, function(e)
print("Error Occured - "..e)
end)
refreshColors(1,1,1)
print(colors[1])
When the refreshColors() function is called, it throws an exception and the error message is "Error Occured - trial.lua:11: attempt to compare number with nil". 当调用refreshColors()函数时,它会抛出异常并且错误消息是“Error Occured - trial.lua:11:尝试将数字与nil进行比较”。 Why the exception occurs although there is no such comparisons in the refreshColors() function?
尽管在refreshColors()函数中没有这样的比较,为什么会发生异常?
The error is on line 11, which means: 错误在第11行,这意味着:
if ccnt < yellowEndIndex then
There's your comparison with a number. 你有一个数字的比较。 We know ccnt is a number (it's initialised at the start of the loop), so yellowEndIndex must be nil.
我们知道ccnt是一个数字(它在循环开始时初始化),所以yellowEndIndex必须是nil。 1 < nil is nonsense so that's an error.
1 <nil是胡说八道,所以这是一个错误。
Since the error message starts with "Error Occured - " we know it must be coming from your try function error handler. 由于错误消息以“Error Occured - ”开头,我们知道它必须来自您的try函数错误处理程序。 This makes sense.
这是有道理的。 You call:
你打电话:
try(refreshColors, function(e)
print("Error Occured - "..e)
end)
try then invokes: 然后尝试调用:
pcall(f)
where f is refreshColours. 其中f是refreshColours。 This invokes refreshColours without any arguments , ie all the arguments are initialised to nil.
这将调用refreshColours 而不带任何参数 ,即所有参数都初始化为nil。 Of course, invoking refreshColouts with a nil value will naturally attempt to compare 1 (ccnt) to nil (yellowEndIndex)!
当然,调用带有nil值的refreshColouts自然会尝试将1(ccnt)与nil(yellowEndIndex)进行比较!
You probably want to modify your try function like so: 你可能想修改你的try函数,如下所示:
function try(f, catch_f, ...)
local status, exception = pcall(f, unpack(arg))
if not status then
catch_f(exception)
end
end
So you can call it like: 所以你可以这样称呼:
try(refreshColours, function(e)
print("Error Occured - "..e)
end), 1, 2, 3);
To pass 1, 2 and 3 in as arguments to refreshColours. 将1,2和3作为参数传递给refreshColours。
Is the error happening because you are calling: 是否因为您正在调用错误而发生错误:
try(refreshColors, function(e) print("Error Occured - "..e) end) 尝试(refreshColors,function(e)print(“Error Occured - ”..e)结束)
and, the refreshColors has no parameters so that it is indeed nil? 并且,refreshColors没有参数,所以它确实是零?
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.