var string = "Hello-Swift"
//獲取某個下標後一個下標對應的字元 char="e"
//swift2.2
//var char = string[startIndex.successor()]
//swift3.0
var char = string[string.index(after: startIndex)]
//獲取某個下標前一個下標對應的字元 char2 = "t"
//swift2.2
//var char2 = string[endIndex.predecessor()]
//swift3.0
var char2 = string[string.index(before: string.endIndex)]
//通過範圍獲取字串中的一個子串 Hello
 

//swift2.2
//var subString = string[startIndex...startIndex.advancedBy(4)]
//swift3.0
var subString = string[startIndex...string.index(startIndex, offsetBy: 4)]
//swift2.2
//var subString2 = string[endIndex.advancedBy(-5)...endIndex.predecessor()]
//swift3.0
var subString2 = string[string.index(endIndex, offsetBy: -5
 
)..<endIndex]
//獲取某個子串在父串中的範圍
//swift2.2
//var range =  string.rangeOfString("Hello")
//swift3.0
var range = string.range(of: "Hello")
//追加字串操作 此時string = "Hello-Swift! Hello-World"
//swift2.2
//string.appendContentsOf(" Hello-World")
//swift3.0
string.append(" Hello-World")
//在指定位置插入一個字元 此時string = "Hello-Swift!~ Hello-World"
 

//swift2.2
//string.insert("~", atIndex: string.startIndex.advancedBy(12))
//swift3.0
string.insert("~", at: string.index(string.startIndex, offsetBy: 12))
//在指定位置插入一組字元 此時string = "Hello-Swift!~~~~ Hello-World"
//swift2.2
//string.insertContentsOf(["~","~","~"], at: string.startIndex.advancedBy(12))
//swift3.0
string.insert(contentsOf: ["~","~","~"], at: string.index(string.startIndex, offsetBy: 12))
//在指定範圍替換一個字串 此時string = "Hi-Swift!~~~~ Hello-World"
//swift2.2
//string.replaceRange(string.startIndex...string.startIndex.advancedBy(4), with: "Hi")
//swift3.0
string.replaceSubrange(string.startIndex...string.index(string.startIndex, offsetBy: 4), with: "Hi")
//在指定位置刪除一個字元 此時string = "Hi-Swift!~~~~ Hello-Worl"
//swift2.2
//string.removeAtIndex(string.endIndex.predecessor())
//swift3.0
string.remove(at: string.index(before:string.endIndex))
//刪除指定範圍的字元 此時string = "Swift!~~~~ Hello-Worl"
//swift2.2
//string.removeRange(string.startIndex...string.startIndex.advancedBy(2))
//swift3.0
string.removeSubrange(string.startIndex...string.index(string.startIndex, offsetBy: 2))
var string2 = "My name is Jaki"
//全部轉換為大寫
//swift2.2
//string2 = string2.uppercaseString
//swift3.0
string2 = string2.uppercased()
//全部轉換為小寫
//swift2.2
//string2 = string2.lowercaseString
//swift3.0
string2 = string2.lowercased()