Controller.swift

import Foundation

protocol CriarUsuarioPresenter: class {
    func success()
    func failed()
}
class CriarUsuario {
    var delegate: CriarUsuarioPresenter?
    
    let api: API = API()
    
    func retornaNomeDoUsuario(user: User) {
        
        let name:String = api.userSignUp(user: user)
        
        if name == "Thiago" {
            self.delegate?.success()
        } else {
            self.delegate?.failed()
        }
    }

}

Networking.swift

import Foundation

//Requisição pro localhost:3333/signIn utilizando model user
protocol ContratoAPI {
    func userSignUp(user: User) -> String
//    Clojure.... completion HTTP 200, 300, 400, 500...
    func userSingIn()
    func userLogout()
}

class API: ContratoAPI {
    func userSignUp(user: User) -> String {
        return user.name
    }
    
    func userSignUp(user: User)  {
        
    }
    
    func userSingIn() {
        
    }
    
    func userLogout() {
        
    }
    
    
}

User.swift

import Foundation

struct User {
    let name: String
    let lastName: String?
    let email: String?
    let password: String
}

ViewController

import UIKit

class ViewController: UIViewController {
    var dataprovider: CriarUsuario = CriarUsuario()
    let user: User = User(name: "Joao", lastName: "", email: "", password: "")
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        self.dataprovider.delegate = self
        dataprovider.retornaNomeDoUsuario(user: user)
    }
    
    func label(name: String) {
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 21))
        label.center = CGPoint(x: 160, y: 285)
        label.textAlignment = .center
        label.text = name
        self.view.addSubview(label)
    }
    
}

extension ViewController: CriarUsuarioPresenter {
    func success() {
        print("\(self.user.name) é foda!")
         self.label(name: self.user.name)
        viewDidAppear(true)
    }
    
    func failed() {
        print("\(self.user.name) é bonitão!")
        
        self.label(name: self.user.name)
    }
    
    
}

ViewController.swift

import UIKit

class ViewController: UIViewController {
    var dataprovider: CriarUsuario = CriarUsuario()
    let user: User = User(name: "Joao", lastName: "", email: "", password: "")
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        self.dataprovider.delegate = self
        dataprovider.retornaNomeDoUsuario(user: user)
    }
    
    func label(name: String) {
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 21))
        label.center = CGPoint(x: 160, y: 285)
        label.textAlignment = .center
        label.text = name
        self.view.addSubview(label)
    }
    
}

extension ViewController: CriarUsuarioPresenter {
    func success() {
        print("\(self.user.name) é foda!")
         self.label(name: self.user.name)
        viewDidAppear(true)
    }
    
    func failed() {
        print("\(self.user.name) é bonitão!")
        
        self.label(name: self.user.name)
    }
    
    
}