User-1.swift

import Foundation
import UIKit

internal class ImageDownloader {
    let url: URL
    init(url: URL) {
        self.url = url
    }

    func fetch(then completion: @escaping (UIImage?, Error?) -> Void) {
        // URL Operation
        // Call completion(image, error)
    }
}

extension UIImage {

    /// Placeholder profile image for the user.
    static let defaultProfileImage: UIImage = UIImage.init(named: "avatar.png")!
}


/// User Model
public class User {
    // Stores the display name for the user model
    public var name: String

    /// Private image holder for the user.
    /// Nil either when image is not there or not fetched.
    var iProfileImage: UIImage?

    /// Display profile image for the user.
    /// Returns either the actual user profile image or the default display image.
    public var profileImage: UIImage {
        return iProfileImage ?? .defaultProfileImage
    }

    init(name:String) {
        self.name = name
    }

    func fetchProfileImage(url: URL, then completion:(Bool)-> Void) {
        let fetcher = ImageDownloader(url: url)
        fetcher.fetch { (image, error) in
            if let fetchError = error {
                print("Failed to fetch Image with error - \(fetchError)")
            } else if let fetchedImage = image {
                print("Image fetched")
                self.iProfileImage = fetchedImage
            } else {
                print("Failed to fetch Image with unknown error")
            }
        }
    }
}