? ?Swift版的Cocoa框架中的API有了大范圍的修改外，Swift的一些核心庫也有了很大的改動奔誓。其中字符串類型String在方法API上更加簡潔，其中變動較大的是與下標相關(guān)的方法搔涝，列舉如下：
var string = "Hello-Swift"
//獲取某個下標后一個下標對應(yīng)的字符 char="e"
var char = string[string.index(after: startIndex)]
//獲取某個下標前一個下標對應(yīng)的字符 char2 = "t"
var char2 = string[string.index(before: string.endIndex)]
//通過范圍獲取字符串中的一個子串 Hello
var subString = string[startIndex...string.index(startIndex, offsetBy: 4)]
var subString2 = string[string.index(endIndex, offsetBy: -5)..<endIndex]
//獲取某個子串在父串中的范圍
var range = string.range(of: "Hello")
//追加字符串操作 此時string = "Hello-Swift! Hello-World"
string.append(" Hello-World")
//在指定位置插入一個字符 此時string = "Hello-Swift!~ Hello-World"
string.insert("~", at: string.index(string.startIndex, offsetBy: 12))
//在指定位置插入一組字符 此時string = "Hello-Swift!~~~~ Hello-World"
string.insert(contentsOf: ["~","~","~"], at: string.index(string.startIndex, offsetBy: 12))
//在指定范圍替換一個字符串 此時string = "Hi-Swift!~~~~ Hello-World"
string.replaceSubrange(string.startIndex...string.index(string.startIndex, offsetBy: 4), with: "Hi")
//在指定位置刪除一個字符 此時string = "Hi-Swift!~~~~ Hello-Worl"
string.remove(at: string.index(before:string.endIndex))
//刪除指定范圍的字符 此時string = "Swift!~~~~ Hello-Worl"
string.removeSubrange(string.startIndex...string.index(string.startIndex, offsetBy: 2))
var string2 = "My name is Jaki"
//全部轉(zhuǎn)換為大寫
string2 = string2.uppercased()
//全部轉(zhuǎn)換為小寫
string2 = string2.lowercased()
