// 字符串的使用
for i in 0..<10{
print(i)
}
for _ in 0...10 {
print("for 循环")
}
// 字符串遍历
let str = "shuxi"
for c in str.characters {
print(c )
}
// 字符串拼接
letstr1 = "xiao gang"
let str2 = "shuxi"
let str3 = str1 + str2
print(str3)
// 字符串与其他标识符的拼接
let name = "hxg"
let age = 20
let height = 1.80
let info = "my name is \(name) age is \(age) height is \(height)"
// 拼接字符串时，字符串的格式化，数字格式化成字符串
let second = 18
let min = 2
let timgStr = String(format:"%.2d:%.2d",arguments:[min,second])
// 字符串截取
let urlStr = "www.baidu.com"
//先将string类型转为NSString类型
//1. 获取.号的索引位置
let index = urlStr.index(str.startIndex,offsetBy:3)
let res = urlStr.substring(to: index)
//2. 截取某个索引位置之后的所有的字符串
let lastRes = urlStr.substring(from: index)
//3.截取某个位置开始长度为N的字符串
let startIndex = urlStr.index(urlStr.startIndex, offsetBy: 3)
let endIndex = urlStr.index(startIndex, offsetBy:2)
let midRes = urlStr.substring(with: startIndex..
// 字符串截取的另一种写法
let head = (urlStr as NSString).substring(to:2)
let mid = (urlStr as NSString).substring(with: NSMakeRange(2,1))
let foot = (urlStr as NSString).substring(to:5)
