lua - 在 Lua 中使用 if、elseif 和 else 重复 Until Loop

Question

我是 Lua 的新手，我一直对这段代码有疑问。它应该使用 io.read 验证用户输入，然后运行正确的 if、elseif 或 else 语句.一旦用户输入正确的响应，代码就应该结束。由于某些原因，代码将只运行初始的 if 语句。任何帮助将不胜感激。

repeat
    resp1 = io.read()

    if resp1 == "Yes" or "yes" then
        print("Well alright then, come on in.")
        print("Let me just take your blood sample like all the rest and you'll be good to go.")
    elseif resp1 == "No" or "no" then
        print("Oh, your not? Then why are you up here?")
        print("Oh nevermind then. None of my business anyways. All I'm supposed to do is take a blood sample for everyone who enters the town.")
        print("So let us get that over with now, shall we?")
    else
        print("Please respond with Yes or No")
    end
until resp1 == "Yes" or resp1 == "No" or resp1 == "no" or resp1 == "yes"

Answer 1

您的问题与此行有关:

if resp1 == "Yes" or "yes" then

这是两个独立的表达式，在 Lua 中，除了 nil 和 false 之外的所有内容都是真值，所以它会选择 if 语句运行，因为 Lua 中的字符串，即使是空字符串，就条件而言，计算结果为 true。如果它有助于你理解，可以这样想:

if (resp1 == "Yes") or ("yes") then

如果您真的想将 resp1 与两个值进行比较，您可以这样做:

if resp1 == "Yes" or resp1 == "yes" then

但是，对于您要实现的目标，这是一个更简单的解决方案:

if resp1:lower() == 'yes' then

---

事实上，您也可以清理循环。使其更具可读性。使用多行字符串而不是多个 print 调用和 break。

repeat
    resp1 = io.read():lower() -- read in lowercased input

    if resp1 == 'yes' then
        print[[Well alright then, come on in.
Let me just take your blood sample like all the rest and you'll be good to go.]]
        break -- exit from the loop here
    elseif resp1 == 'no' then
        print[[Oh, your not? Then why are you up here?
Oh nevermind then. None of my business anyways. All I'm supposed to do is take a blood sample for everyone who enters the town.
So let us get that over with now, shall we?]]
        break
    else
        print'Please respond with Yes or No'
    end

until false -- repeat forever until broken