Lua_多重排序

网上有好多排序，不过写的都大同小异。本文讲解下多重排序，意思是多个条件排序。 
前提： 
1.Lua排序的原理是冒泡排序,即从前往后比较,满足一定条件A则交换,否则不交换。 

2.Lua排序函数table.sort(tbl, sortFunc), sortFunc中会比较前后表中前后两个值,sortFunc函数返回true则不交换,返回false则交换。 

例子：

table_demo = {
	[1] = {
		age = 18,
		height = 1.6,
		weight = 100,
	},
	[2] = {
		age = 13,
		height = 1.5,
		weight = 80,
	},
	[3] = {
		age = 14,
		height = 1.7,
		weight = 120,
	},
	[4] = {
		age = 11,
		height = 1.6,
		weight = 110,	
	},
	[5] = {
		age = 18,
		height = 1.6,
		weight = 90,	
	},
}

local function sortFunc(a, b)
    if a.age == b.age then
        if a.height == b.height then
            return a.weight < b.weight
        else
            return a.height < b.height
        end
    else
        return a.age < b.age
    end
end

--目标：将table_demo 按照age从小到大排序, 若age大小相等则按照height从小到大排序, 如果height一样大,则按weight从小到大排序
table.sort(table_demo, sortFunc)

for k=1, 5 do
    print(string.format("k:%d   age:%d   height:%.1f   weight:%d", k, table_demo[k].age, table_demo[k].height, table_demo[k].weight))
end