//基类，人类
class Human{
}

//男人类
class Man:human{
}

//女人类
class Woman:human{
}

1，is 用来做类型检查
（注意：is也可以用来检查某个类是否遵循了某个协议）

let man = Man()
let woman = Woman()
var arr = [man,woman]

for people in arr {
	if people is Man {
		println("这是个男人")
	}else if people is Woman {
		println("这是个女人")
	}
}

2，as 用来做类型转换
（注意：如果不确定类型转换能否成功，可以在as后面加问号“?”）

let man = Man()
let woman = Woman()
var arr = [man,woman]

for people in arr {
	if let m = people as? Man {
		println("这是个男人")
	}else if let w = people as? Woman {
		println("这是个女人")
	}
}