Add Async image loading

Examples/Async image loading/RemoteImage/ImageLoader.swift

@@ -0,0 +1,59 @@
+//
+//  File 2.swift
+//  
+//
+//  Created by Callum Trounce on 05/06/2019.
+//
+
+import Foundation
+import SwiftUI
+import Combine
+
+@available(iOS 13.0, *)
+class ImageLoader {
+    
+    static let shared = ImageLoader()
+    
+    private let fileManager = FileManager()
+    
+    private let cache = ImageCache()
+    
+    private lazy var session = URLSession.init(configuration: .default)
+    
+    public func load(url: URL, result: @escaping ((CGImage) -> Void)) {
+        
+        if let cachedImage = cache.image(for: url) {
+            result(cachedImage)
+            return
+        }
+        
+        let request = session.downloadTask(with: url, completionHandler: { [weak self] (downloadLocation, response, error) in
+            self?.handleDownload(response: response!, location: downloadLocation!, result: result)
+        })
+        
+        request.resume()
+    }
+
+    func handleDownload(response: URLResponse, location: URL, result: @escaping ((CGImage) -> Void)) {
+        guard let url = response.url else { return }
+        do {
+            let directory = try fileManager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true).appendingPathComponent(location.lastPathComponent)
+            try fileManager.copyItem(at: location, to: directory)
+            
+            guard
+                let imageSource = CGImageSourceCreateWithURL(directory as NSURL, nil) else {
+                    fatalError("couldn't create image source")
+            }
+
+            guard let image = CGImageSourceCreateImageAtIndex(imageSource, 0, nil)
+                else {
+                    fatalError("Couldn't load image \(directory)")
+            }
+            
+            cache.store(image: image, for: url)
+            result(image)
+        } catch {
+            fatalError(error.localizedDescription)
+        }
+    }
+}