【进阶实战】接口契约：模块间调用的参数校验层

local function checkContract(args, contract, fnName)
    for _, field in ipairs(contract) do
        local name, ptype, required = field[1], field[2], field[3]
        local v = args[name]
        if v == nil or v == "" then
            if required then
                error(fnName .. " 缺少必填参数：" .. name)
            end
        else
            local actual = type(v)
            if actual ~= ptype then
                if not (ptype == "number" and actual == "string"
                    and tonumber(v)) then
                    error(fnName .. " 参数 " .. name .. " 应为 "
                        .. ptype .. "，实际 " .. actual)
                end
            end
        end
    end
end
local SEND_CONTRACT = {
    { "to", "string", true },
    { "itemId", "string", true },
    { "num", "number", true },
    { "reason", "string", false },
}
local function sendAwardMail(args)
    checkContract(args, SEND_CONTRACT, "sendAwardMail")
    sendmail("#" .. args.to, 0, "奖励发放", args.reason or "",
        args.itemId .. "," .. args.num)
    return true
end

sendAwardMail({ to = "无名小卒", itemId = "裁决之杖", num = "1" })