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Delegate Example in swift

 Add Two Number With Simple Delegate - Swift delegate protocol is with simple examples to understand the delegate pattern using protocols in swift.


        import UIKit

        import PlaygroundSupport


        PlaygroundPage.current.needsIndefiniteExecution = true

        class Developer {

            var manager: Manager?

            func developerWillAddTwoNumbers(a: Int, b: Int){

                let result = a + b

                manager?.addTwoNumber(result: result)



        class Manager {

            var developer: Developer?


            init (_develoepr: Developer){

                self.developer = _develoepr

                developer?.manager = self



            func addTwoNumber(result: Int){

                print("Result: === \(result)")



            func add(x: Int, y: Int){

                developer?.developerWillAddTwoNumbers(a: x, b: y)



        let objManager = Manager(_develoepr: Developer())

        objManager.add(x: 10, y: 5)

Download Image With Delegate  & protocol

        import UIKit

        import PlaygroundSupport

        PlaygroundPage.current.needsIndefiniteExecution = true

        struct Images {

        static let imageUrl = ""


        protocol ImageDownloadDlegate : AnyObject {


        func didFinishedDownloadImage(result: Data?)



        class ImageDownloader {


           weak var imageDownloadDlegate: ImageDownloadDlegate?


            func downloadImageServer(url: URL){

                URLSession.shared.dataTask(with: url) { imageData, response, error in

                    self.imageDownloadDlegate?.didFinishedDownloadImage(result: imageData)




        class ImageViewer: ImageDownloadDlegate {

            var imageDownloader: ImageDownloader?


            init(_imageDownloader: ImageDownloader){

                self.imageDownloader = _imageDownloader

                imageDownloader?.imageDownloadDlegate = self

                imageDownloader?.downloadImageServer(url: URL(string: Images.imageUrl)!)



            func didFinishedDownloadImage(result: Data?) {

                let image = UIImage(data: result!)




        let objImageViewer = ImageViewer(_imageDownloader: ImageDownloader())


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