Swift 4.0 字符串(String)学习

定义字符串常量(常量只有读操作)

    let lString = "constant"    let lString1: String = "constant"

定义字符串变量

    var string = ""    var string1: String = "哈哈"    var string2 = String()

赋值

    string = "this-is-a-string-variable"

字符串分割

 let stringArray = string.split(separator: "-") // 按'-'分割 print(stringArray) // ["this", "is", "a", "string", "variable"]

字符串截取

 let start = string.startIndex  // 开始下标 let end = string.index(string.startIndex, offsetBy: 7) // 结束下标 let subString = string[start ..< end] print(subString)   // this-is

1、string.startIndex 表示第一个字符的下标
2、string.endIndex 表示最后一个字符的下标
3、startIndex、endIndex是Index类型，不是Int类型

字符串拼接

string += "!"       // 追加'!'print(string)       // this-is-a-string-variable!string += string1   // 追加字符串变量string1print(string)       // this-is-a-string-variable!哈哈let num = 100string = string + "--\(num)"print(string)       // this-is-a-string-variable!哈哈--100