Delegate method not called using Singleton - delegates

Question

Similar questions have already been asked but they haven't helped. I'm trying to call protocol method declared in Singleton class from a view controller but the called method never invokes.
My protocol and class are:
import Foundation
protocol ServiceDelegate {
func serviceData(data: [String: Any])
}
class Service {
private static let sharedInstance = Service() // singleton object
var delegate: ServiceDelegate?
class func shared() -> Service {
return sharedInstance
}
func login(postData:String) {
let url = URL(string: "MY_URL")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
let dataBody = postData.data(using:String.Encoding.ascii, allowLossyConversion: false)
request.httpBody = dataBody
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
guard let data = data, error == nil else {
print(error?.localizedDescription ?? "No data")
return
}
let responseJSON = try? JSONSerialization.jsonObject(with: data, options: [])
if let dataArray = responseJSON as? [String: Any] {
self.delegate?.serviceData(data: dataArray) // This is getting called
}
}
task.resume()
}
}
My view controller class where protocol is implemented is:
import UIKit
class LoginVC: UIViewController, ServiceDelegate {
var serviceInstance: Service = Service()
override func viewDidLoad() {
super.viewDidLoad()
serviceInstance.delegate = self
}
#IBAction func loginBtn(_ sender: Any) {
let info = "userName=\(String(describing: usernameText.text!))&password=\(String(describing: passwordText.text!))"
Service.shared().login(postData: info)
}
// This is not getting called:
func serviceData(data: [String : Any]) {
print(data)
}
Is the above implementation correct? Can I use private singleton object to successfully implement protocol method?

Answer 1

You are creating two Service instances. You should only be using the one returned by Service.shared(). That’s the actual singleton shared across your app.
In your view controller, replace this line:
serviceInstance.delegate = self
with:
Service.shared().delegate = self
And you should also delete this line (i.e., the unnecessary second instance):
var serviceInstance: Service = Service()