Add Async image loading

Examples/Async image loading/RemoteImage/ImageCache.swift

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+//
+//  File 2.swift
+//  
+//
+//  Created by Callum Trounce on 05/06/2019.
+//
+
+import Foundation
+import SwiftUI
+
+@available(iOS 13.0, *)
+class ImageCache {
+    
+    private let cache = NSCache<NSURL, CGImage>()
+    
+    private let queue = DispatchQueue.init(label: "cacheQueue", qos: .userInteractive)
+    
+    func store(image: CGImage, for url: URL) {
+        queue.async { [unowned cache] in
+            cache.setObject(image, forKey: url as NSURL)
+        }
+    }
+    
+    func image(for url: URL) -> CGImage? {
+        return cache.object(forKey: url as NSURL)
+    }
+}

Examples/Async image loading/RemoteImage/ImageLoader.swift

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+//
+//  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)
+        }
+    }
+}

Examples/Async image loading/RemoteImage/RemoteImage.swift

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+//
+//  RemoteImage.swift
+//  Landmarks
+//
+//  Created by Callum Trounce on 06/06/2019.
+//  Copyright © 2019 Apple. All rights reserved.
+//
+
+import Foundation
+import SwiftUI
+import Combine
+
+@available(iOS 13.0, *)
+class RemoteImage: BindableObject {
+
+    var didChange = PassthroughSubject<Image?, Never>()
+
+    typealias PublisherType = PassthroughSubject<Image?, Never>
+
+    var image: Image? = nil {
+        didSet {
+            guard oldValue != image else { return }
+            DispatchQueue.main.async {
+                self.didChange.send(self.image!)
+            }
+        }
+    }
+
+    func load(url: URL) -> Self {
+        guard image == nil else { return self }
+        ImageLoader.shared.load(url: url) { [unowned self] (image) in
+            let final = Image.init(image, scale: 1, label: Text(url.lastPathComponent))
+            self.image = final
+        }
+        return self
+    }
+}

Examples/Async image loading/RemoteImage/RemoteImageView.swift

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+//
+//  RemoteImageView.swift
+//  Landmarks
+//
+//  Created by Callum Trounce on 06/06/2019.
+//  Copyright © 2019 Apple. All rights reserved.
+//
+
+import Foundation
+import SwiftUI
+
+@available(iOS 13.0, *)
+public struct RemoteImageView: View {
+    
+    var url: URL
+    
+    var placeholderImage: Image?
+    
+    @State
+    var remoteImage: RemoteImage = RemoteImage()
+    
+    public var body: some View {
+        return (remoteImage.load(url: url).image ?? placeholderImage)?.resizable()
+    }
+    
+    public init(url: URL, placeholderImage: Image? = nil) {
+        self.placeholderImage = placeholderImage
+        self.url = url
+    }
+}

Examples/Async image loading/SwURL.swift

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+struct SwURL {
+    
+    
+    
+}