【Lua实战】元表写入拦截：__newindex只读表的实现细节

local function readonly(t)
    local proxy = {}
    setmetatable(proxy, {
        __index = t,
        __newindex = function(_, k)
            error("readonly table, attempt to write key: " .. tostring(k), 2)
        end,
        __metatable = "locked",
    })
    return proxy
end
local CONFIG = readonly({ dropRate = 100, warTime = 3600 })

local WRITABLE = { runtimeFlag = true }
local function safeWrite(t, k, v)
    if WRITABLE[k] then
        rawset(t, k, v)
        return true
    end
    error("key not writable: " .. tostring(k), 2)
end