一个循环遍历多个Lua表 [英] One loop for iterating through multiple Lua tables

问题描述

是否可以在同一循环中遍历多个Lua表?

Is it possible to iterate through multiple Lua tables with the same loop?

要遍历索引表，我可以执行以下操作:

For looping through indexed tables I can do something like this:

local t1 = {"a", "b", "c"}
local t2 = {"d", "e", "f"}

local num = #t1+#t2
for i=1, num, do
    local j
    local val
    if i <= #t1 then
        j = i
        val = t1[j]
    else
        j = i-#t1
        val = t2[j]
    end

    -- Do stuff
end

但是键值表呢?

例如像这样的东西:

local t1 = {a="a", b="b", c="c"}
local t2 = {d="d", e="e", f="f"}

for key, val in pairs(t1) or pairs(t2) do
    print(key..":  '"..val.."'")
end

应导致以下结果:

a:  'a'
b:  'b'
c:  'c'
d:  'd'
e:  'e'
f:  'f'

推荐答案

function pairs(t, ...)
  local i, a, k, v = 1, {...}
  return
    function()
      repeat
        k, v = next(t, k)
        if k == nil then
          i, t = i + 1, a[i]
        end
      until k ~= nil or not t
      return k, v
    end
end

local t1 = {a="a", b="b", c="c"}
local t2 = {d="d", e="e", f="f"}

for key, val in pairs(t1, t2) do
    print(key..":  '"..val.."'")
end

注意:此实现不遵守__pairs元方法.

Note: this implementation does not respect __pairs metamethod.

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