类型方法:属于类型本身，无需实力话就可以使用，方法前加关键字 static
对于类，加关键字class 可被子类重写(override)
class Player {
static var nick = "xiaobo"
class func server() {
print("\(nick),您在北京联通1区")
}
}
Player.server()
class ShangHaiPlayer : Player {
override static func server() {
print(nick,"您在上海电信2区")
}
}
class WuHanPlayer : Player {
override static func server() {
print("\(nick),您在武汉电信3区")
}
}
ShangHaiPlayer.server()
WuHanPlayer.server()
