A summary of changes brought by Swift 3.0

 var string = "Hello-Swift"
//Get the character corresponding to the subscript after a subscript char="e"//swift2.2
//var char = string[()]
//swift3.0
var char = string[(after: startIndex)]
//Get the character corresponding to the previous subscript of a subscript char2 = "t"//swift2.2
//var char2 = string[()]
//swift3.0
var char2 = string[(before: )]
//Get a substring in a string through range Hello//swift2.2
//var subString = string[startIndex...(4)]
//swift3.0
var subString = string[startIndex...(startIndex, offsetBy: 4)]
//swift2.2
//var subString2 = string[(-5)...()]
//swift3.0
var subString2 = string[(endIndex, offsetBy: -5)..<endIndex]
//Get the range of a child string in the parent string//swift2.2
//var range = ("Hello")
//swift3.0
var range = (of: "Hello")
//Add string operation At this time string = "Hello-Swift! Hello-World"//swift2.2
//(" Hello-World")
//swift3.0
(" Hello-World")
//Insert a character at the specified position At this time string = "Hello-Swift!~ Hello-World"//swift2.2
//("~", atIndex: (12))
//swift3.0
("~", at: (, offsetBy: 12))
//Insert a set of characters at the specified position At this time string = "Hello-Swift!~~~ Hello-World"//swift2.2
//(["~","~","~"], at: (12))
//swift3.0
(contentsOf: ["~","~","~"], at: (, offsetBy: 12))
//Replace a string in the specified range At this time string = "Hi-Swift!~~~ Hello-World"//swift2.2
//(...(4), with: "Hi")
//swift3.0
(...(, offsetBy: 4), with: "Hi")
//Delete a character at the specified location At this time string = "Hi-Swift!~~~ Hello-Worl"//swift2.2
//(())
//swift3.0
(at: (before:))
//Delete characters in the specified range At this time string = "Swift!~~~~ Hello-Worl"//swift2.2
//(...(2))
//swift3.0
(...(, offsetBy: 2))
var string2 = "My name is Jaki"
//Convert all to uppercase//swift2.2
//string2 = 
//swift3.0
string2 = ()
//Convert all to lowercase//swift2.2
//string2 = 
//swift3.0
string2 = ()