【入门夯实】嵌套取值的nil链：中间环节的判空写法

local cfg = { gong = { rate = 5 } }
print(cfg.gong.boss.rate)

local function safeGet(t, ...)
    local cur = t
    for _, k in ipairs({ ... }) do
        if type(cur) ~= "table" then
            return nil
        end
        cur = cur[k]
    end
    return cur
end
local cfg = { gong = { rate = 5 } }
print(safeGet(cfg, "gong", "boss", "rate"))

local function getOr(t, def, ...)
    local v = safeGet(t, ...)
    if v == nil then
        return def
    end
    return v
end
local cfg = { gong = { rate = 5 } }
print(getOr(cfg, 10, "gong", "boss", "rate"))