运算符变化
>>>>>>3.0
var add = 2;
add += 1;
add -= 1;
>>>>>>>2.3
var add = 2;
add++;
add--;
selector的swift风格化
>>>>>>>>>>3.0
btn.addTarget(self, action:#selector(ViewController.click), forControlEvent: UIControlEvent.TouchUpInside)
>>>>>>>>>>2.3
btn.addTarget(self, action:"click", forControlEvent: .TouchUpInside)
枚举变化 (首字母小写)
>>>>>>>>>3.0
enum Direction: String {
case east = "east"
case south = "south"
case west = "west"
case north = "north"
}
>>>>>>>>>2.3
enum Direction: String {
case East = "east"
case South = "south"
case West = "west"
case North = "north"
}