swift字符串

定义字符串

let a : String = "hello world"
let b = "hello"

遍历字符串

for c in str {
    print(c)
}

字符串之间的拼接

let str1 = "da"
let str2 = "jia"
let str3 = "hao"
let totalStr = str1 + str2 + str3 

字符串和其他标识符之间的拼接

let name = "lxd"
let age = 24
let height = 188
let myInfo = "my name is \(name),my name is \(age),my name is \(height)" 
print(myInfo)
//输出my name is lxd, my age is 24, my height is 188

字符串的格式化

let minutes = 6
let seconds = 33
let time = String(format: "%02d:%02d", arguments: [minutes, seconds])
print(time)
//输出06:33

截取字符串

let urlStr = "www.baidu.com"

let prefixStr = urlStr.prefix(3) 
print(prefixStr) //输出www

let suffixStr = urlStr.suffix(3)
print(suffixStr) //输出com

let range = NSRange(location: 4, length: 5)
let middleStr = (urlStr as NSString).substring(with: range)
print(middleStr) //输出baidu