? ?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。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的方法，列舉如下：

var string = "Hello-Swift"

//獲取某個下標后一個下標對應的字符 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"

//全部轉換為大寫

string2 = string2.uppercased()

//全部轉換為小寫

string2 = string2.lowercased()