CustomImageView.swift

enum ImageDownloadError: Error {
	case url(errorDescription: String)
	case data(errorDescription: String)
}

class CustomImageView: UIImageView {
	var downloadTask: URLSessionDataTask?
	
	func loadImageUsing(urlString string: String,
						finishedLoadingImage: @escaping (Error?) -> ()) {
		
		guard let url = URL(string: string) else {
			finishedLoadingImage(ImageDownloadError.url(errorDescription: "cant construct url using: \(string)"))
			return
		}
		
		do {
			if let imageData = try AssetSaveHelper.cachedDataForTag("\(string.hashValue)") {
				self.image = UIImage(data: imageData)
				finishedLoadingImage(nil)
				return
			}
		} catch let err {
			print(err)
		}
		
		downloadTask = URLSession.shared.dataTask(with: url) {
			[weak self] (data, response, error) in
			guard let httpResponse = response as? HTTPURLResponse,
				(200 ... 299).contains(httpResponse.statusCode),
				let data = data else {
					finishedLoadingImage(ImageDownloadError.data(errorDescription: ""))
					return
			}
			DispatchQueue.main.async { [weak self] in
				self?.image = UIImage(data: data)
				try? AssetSaveHelper.cacheDataForTag(data, tag: "\(string.hashValue)")
				finishedLoadingImage(nil)
			}
		}
		downloadTask?.resume()
	}
}