User-2.swift

/// Injecting fetcher to the fetch API, so that we get control of downloading outside of the User class
func fetchProfileImage(fetcher: ImageDownloader, then completion: @escaping (Bool)-> Void) {
    fetcher.fetch { (image, error) in
        if let fetchError = error {
            print("Failed to fetch Image with error - \(fetchError)")
            completion(false)
        } else if let fetchedImage = image {
            print("Image fetched")
            self.iProfileImage = fetchedImage
            completion(true)
        } else {
            print("Failed to fetch Image with unknown error")
            completion(false)
        }
    }
}

// And you can use it like this
let currentUser = User(name: "Tim Cook")
let imageFetcher = ImageDownloader(url: URL(string: "https://somerandomapp.mlaz.im/images/GkdhaKGjhgj7yjHo")!)
currentUser.fetchProfileImage(fetcher: imageFetcher) { (downloaded) in
    if downloaded {
        print("Yay!! Show it somewhere!")
    } else {
        print("Ooops! Failed to download you image!")
    }
}