Reactive ImageDownloader with Alamofire + Cache

ImageDownloader.swift

//
//  ImageDownloader.swift
//  ImageDownloader
//
//  Created by Oluwatobi Omotayo on 27/05/2020.
//  Copyright © 2020 Oluwatobi Omotayo. All rights reserved.
//

import UIKit
import RxSwift
import Alamofire

class ImageCache {
    var cacheDictionary = Dictionary<String, UIImage>()
    
    func saveImageToCache(image: UIImage?, url: URL) {
        if let image = image {
            cacheDictionary[url.absoluteString] = image
        }
    }
    
    func imageFromCacheWith(url: URL) -> UIImage? {
        return cacheDictionary[url.absoluteString]
    }
}

class ImageDownloader {
    enum Errors: Error {
        case noImageData
    }
    
    static let shared = ImageDownloader()
    let cache: ImageCache
    
    private init(cache: ImageCache = ImageCache()) {
        self.cache = cache
    }
    
    func downloadImage(from url: URL) -> Observable<UIImage> {
        return Observable.create {[unowned self] observer -> Disposable in
            if let image = self.cache.imageFromCacheWith(url: url) {
                observer.onNext(image)
                observer.onCompleted()
            } else {
                AF.download(url).responseData { response in
                    let result = response.result
                    switch result {
                    case .success(let data):
                        if let image = UIImage(data: data) {
                            self.cache.saveImageToCache(image: image, url: url)
                            observer.onNext(image)
                            observer.onCompleted()
                        } else {
                            observer.onError(Errors.noImageData)
                        }
                    case .failure(let error):
                        observer.onError(error)
                    }
                }
            }
            return Disposables.create()
        }
    }
}