// for-in 遍历String
for c in str.characters{
  print(c)
}
//c是Character类型

// Character和String的相互转换
//let mark = "!" //此时mark是String类型
let mark: Character = "!" //Character必须要显示声明
//str + mark //类型不同拼接会报错
str + String(mark) //进行类型转换后再拼接

// append 相当于 +=
str.append(mark)
//var类型才可以调用append方法，let类型不可以

// Characters是基于Unicode的
let englishLetter: Character = "a"
let chineseLetter: Character = "哈"
let dog: Character = "��"
let coolGuy = "\u{1F60E}"

// String对Unicode的支持
var coolLetters = "abc" //abc
coolLetters.characters.count //3

var chineseLetters = "你好吗" //你好吗
chineseLetters.characters.count //3

var coolGuys = "\u{1F60E}\u{1F60E}\u{1F60E}" //������
coolGuys.characters.count //3

var cafe = "café" //café
var cafe2 = "cafe\u{0301}" //café
cafe.characters.count //4
cafe2.characters.count //4


// String的比较
cafe == cafe2