【Lua实战】多继承 mixin：给装备系统混入可交易能力

---可交易 mixin：交易相关的方法
local TradeMixin = {
    canTrade = function(self) return not self.binded end,
    getTradePrice = function(self) return self.tradePrice end,
}

---可强化 mixin：强化相关的方法
local EnhanceMixin = {
    enhance = function(self, level)
        self.enhanceLevel = level
    end,
}

---混入：把 mixin 的键复制到目标表
local function mixin(target, ...)
    for _, m in ipairs({...}) do
        for k, v in pairs(m) do
            if rawget(target, k) == nil then
                rawset(target, k, v)
            end
        end
    end
    return target
end

local equipMt = {}
mixin(equipMt, TradeMixin, EnhanceMixin)

---冲突检测：同名键的警告
local function mixinWithCheck(target, source, name)
    local conflicts = {}
    for k, v in pairs(source) do
        if rawget(target, k) ~= nil then
            conflicts[#conflicts + 1] = k
        end
    end
    if #conflicts > 0 then
        Ops.alert('mixin 冲突: ' .. name, table.concat(conflicts, ','))
    end
    for k, v in pairs(source) do
        rawset(target, k, v)
    end
end