swift 字符串String的基本用法

1、声明

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")

2、判断字符串是否为空

// 判断空字符串str.isEmpty    //falseemptyString.isEmpty  //true

3、字符串拼接

// String的粘合let mark = "!!!"str + mark   //Hello, playground!!!str  //Hello, playground// 常量String和变量Stringstr += mark  str  //Hello, playground!!!//str2 += mark  //let 会报错

4、字符串插值

// 字符串插值let name = "lxy"let age  = 18let height = 1.78let 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.

5、特殊字符

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