import UIKit

//swift 字串
//1>swift中的字串String是一個結構體，效能更高
//2>NSString是一個OC物件，效能略差
//3>String支援直接遍歷
//4>Swift提供了String和NSString的無縫轉換
let str = "hello world"

//遍歷字串
for c in str.characters{
    print(c)
}

//字串拼接
//兩個字串之間的拼接
let str1 = "你好"

let str2 = "世界"

let str3 = str1 + str2

//字串和其它識別符號的拼接
let name = "ZYF"

let age = 18

let height = 1.88

let info = "my name is \(name) , my age is \(age) , my height is \(height)"

//拼接字串時，字串的格式化
let minent = 2

let seconds = 8

let timeString = String(format: "%02d:%02d", arguments:[minent,seconds])

print(timeString)

//字串的擷取
let urlStr = "www.zhengyanfeng.com"

//將String型別轉換為NSString型別


let header = (urlStr as NSString).substring(to: 3)

let body = (urlStr as NSString).substring(with: NSRange(location: 4, length: 12))

let afterbody = (urlStr as NSString).substring(from: 17)