swift 字符串索引 删除字符串 插入字符串

1//: A UIKit based Playground for presenting user interface
2  
3import UIKit
4//字符串索引
5let greeting  = "Guten Tag!"
6greeting[greeting.startIndex]
7greeting[greeting.index(before: greeting.endIndex)]
8
9greeting[greeting.index(after: greeting.startIndex)]
10let index = greeting.index(greeting.startIndex,offsetBy: 7)
11greeting[index]
12
13
14//插入
15var welcome = "Hello"
16welcome.insert("!", at: welcome.endIndex)
17welcome.insert(contentsOf:"there",at: welcome.index(before: welcome.endIndex))
18//删除
19welcome.remove(at: welcome.index(before: welcome.endIndex))
20
21let range = welcome.index(welcome.endIndex, offsetBy: -6)..<welcome.endIndex
22welcome.removeSubrange(range)
23
24