【高级技巧】组合模式：整体与部分的同一接口设计

local function newUnit(name, power)
    return { name = name, power = power,
        getPower = function(self) return self.power end }
end
local function newGroup(name, units)
    return { name = name, members = units,
        getPower = function(self)
            local total = 0
            for _, u in ipairs(self.members) do
                total = total + u:getPower()
            end
            return total
        end }
end

local m1 = newUnit("甲", 1000)
local m2 = newUnit("乙", 1200)
local team = newGroup("一队", { m1, m2 })
local guild = newGroup("行会", { team, newUnit("散修", 800) })
print(guild:getPower())