A little helper for downloading images

WUImageDownloader.swift

//
//  WUImageDownloader.swift
//  WorkUp
//
//  Created by Simon Lebedev on 9/6/17.
//  Copyright © 2017 Simon. All rights reserved.
//

import UIKit
import AlamofireImage

private let downloader = ImageDownloader()
private let downloaderNotCached = ImageDownloader(configuration: URLSessionConfiguration.default,
                                                  downloadPrioritization: .fifo, maximumActiveDownloads: 4, imageCache: nil)

//Preferable use this method to download images because it caches images
//except for case where server you use does not provide unique URLs
//for images which were just modified. In this case use downloadImageNotCached
func downloadImage(path: String?, completion: @escaping (UIImage?) -> ()) {
    guard let urlRequest = prepareURLRequest(forPath: path, completion: completion) else { return }
    downloader.download(urlRequest) { response in
        completion(response.result.value)
    }
}

func downloadImageNotCached(path: String?, completion: @escaping (UIImage?) -> ()) {
    guard let urlRequest = prepareURLRequest(forPath: path, completion: completion) else { return }
    downloaderNotCached.download(urlRequest) { response in
        completion(response.result.value)
    }
}

private func prepareURLRequest(forPath: String?, completion: @escaping (UIImage?) -> ()) -> URLRequest? {
    guard let path = forPath else {
        completion(nil)
        return nil
    }
    guard let url = URL(string: path) else {
        completion(nil)
        return nil
    }
    return URLRequest(url: url)
}