Whats new in swift 4

Swift 4.0 is a major new release for everyone’s favorite app development language, and introduces a variety of features that let us write simpler, safer code. Swift 4 release is designed around two primary goals: to provide source stability for Swift 3 code and to provide ABI stability for the Swift standard library

WARNING:Swift 4 is still under active development.Please keep in mind that more features are likely ship in the months before final release.

Multi-Line String Literals — SE-0168

Adding new lines using n and escaping double quotes in string is not always pleasant task.

let multiLineString = """This is one of the best feature add in Swift 4It let’s you write “Pradeep Chauhan” new lines without need of “n”"""print(multiLineString)

Smart KeyPaths: Key-Value Coding — SE-0161

You can grab root object name and drill down upto any property name to get its value. Key path starts with operator.

struct Address {  var city:String  var state:String}struct User {  var name: String  var addresses: [Address]    var primaryAddress: Address {      return addresses.first!  }}

Now If we have friend object and want to get the value then following key path syntax should be used.

print(user[keyPath:User.primaryAddress.state])

Swift Archival & Serialization — SE-0166

Good News! Swift 4 comes with built in encoders and decoders for JSON. JSON <-> Model conversion is comes built in ( Although you can customize that behavior if required ).
Swift 4 introduces a newCodableprotocol that lets you serialize and deserialize custom data types without writing any special code –and without having to worry about losing your value types. Even better, you can choose how you want the data to be serialized: you can use classic property list format or even JSON.

struct Address:Codable {  var city:String  var state:String}struct User: Codable {  var name: String  var address: Address}

Encoding ( Model -> JSON )

Let's fill out some detailslet address = Address(city: "Udaipur", state: "Rajasthan")let user = User(name: "pradeep Chauhan", address: address)let encoder = JSONEncoder() // Define JSONEncoderif let encoded = try? encoder.encode(user) {  if let json = String(data: encoded, encoding: .utf8) {    print(json)  }}

Decoding ( JSON -> Model )

let decoder = JSONDecoder()if let decoded = try? decoder.decode(User.self, from: encoded) {  print(decoded.name)  print(decoded.address)}

Strings are collections again — SE-0163

This is a small change, but one guaranteed to make a lot of people happy: strings are collections again. This means you can reverse them, loop over them character-by-character,map()andflatMap()them, and more. For example:

let str = "What's new in swift 4"for ch in str {    print(ch)}

MutableCollection.swapAt—SE-0173

New swap function now takes indices of elements which are to be swapped.

var list = ["Pradeep","Chauhan","iOS","Developer"]list.swapAt(1,2)Output.["Pradeep","iOS","Chauhan","Developer"]

One-sided Ranges—SE-0172

Now we can use one side range where missing side will automatically treated as start or end of sequence.

let list = ["Pradeep","Chauhan","iOS","Developer"]let firstTwo = names[..<2]let lastThree = names[1…]print(firstTwo)print(lastThree)Which will produce following output.["Pradeep", "Chauhan"] // [..<2] => [0,1]["Chauhan","iOS","Developer"] // list[2…] => [1,2,3]

Dictionary and Set enhancements—SE-0165

1. you can create a dictionary using array elements.

   let users = ["Ajay", "Ratish", "Vishal"]let usersDictionary = Dictionary(uniqueKeysWithValues: zip(1…, users))print(usersDictionary)

   Which will produce following output.

   ["0":"Ajay", "1":"Ratish", "2":"Vishal"]