var str = "Hello, playground"
//var str: String = "Hello, playground"


// 空字符串
let emptyString = ""
let emptyString2 = String()


// 使用String()初始化字符串
let str2 = String("Hello, swift")

// 判断空字符串
str.isEmpty //false
emptyString.isEmpty //true

// String的粘合
let mark = "!!!"
str + mark //Hello, playground!!!
str //Hello, playground


// 常量String和变量String
str += mark 
str //Hello, playground!!!

//str2 += mark //let 会报错

// 字符串插值
let name = "lxy"
let age = 18
let height = 1.78
let s = "My name is \(name), I'm \(age) years old. I'm \(height) meters tall."
print(s) //My name is lxy, I'm 18 years old. I'm 1.78 meters tall.

// 特殊字符
let s = "\\" =>\
let s = "\"" =>"
let s = "\n" =>换行