Optional Variables in protocol is possible?

Question

protocol AProtocol: BProtocol {     /// content to be shown on disclaimer Label of cell     var disclaimer: String {get set}     var cellDisclaimerAttributed: NSAttributedString {get}     var showSelection: Bool {get set}     var isReadMore: Bool {get} } 

I want to make variables optional so that I need not implement all variables every time after conforming protocol. Like in Objective-C we did for methods:

protocol AProtocol: BProtocol {     /// content to be shown on disclaimer Label of cell     optional var disclaimer: String {get set}     optional var cellDisclaimerAttributed: NSAttributedString {get}     optional var showSelection: Bool {get set}     optional var isReadMore: Bool {get} } 

Is it possible?

Answer 1

protocol TestProtocol {     var name : String {set get}     var age : Int {set get} } 

Provide a default extension for the protocol. Provide the default implementation for all the variables set and get which u want them to be optional.

In below protocol, name and age are optional.

 extension TestProtocol {      var name: String {         get { return "Any default Name" } set {}     }       var age : Int { get{ return 23 } set{} }       } 

Now if I am conforming above protocol to any other class, like

class TestViewController: UIViewController, TestProtocol{         var itemName: String = ""  **I can implement the name only, and my objective is achieved here, that the controller will not give a warning that "TestViewController does not conform to protocol TestProtocol"**     var name: String {         get {             return itemName ?? ""         } set {}     } } 

Answer 2

If you want to conform to Swift's documentation, you'd have to implement it like this :

@objc protocol Named {     // variables     var name: String { get }     @objc optional var age: Int { get }        // methods     func addTen(to number: Int) -> Int     @objc optional func addTwenty(to number: Int) -> Int }  class Person: Named {     var name: String          init(name: String) {         self.name = name     }          func addTen(to number: Int) -> Int {         return number + 10     } }