swift -- typealias---Int

typealias;给某个类型取个别名,和oc中给block起个别名类似

UInt8：0~255 (0~2^8)
Int8：-256~255 (-2^8 ~ 2^8-1)

Int16 , Int32, Int64类似

typealias HZ = UInt8;

var value:HZ;

value = 255; //256会报错

print(value)