pokedex demo

Demo/Sources/Helpers/NetworkImageView.swift

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+//
+// Demo
+// Copyright © 2020 John Rommel Estropia, Inc. All rights reserved.
+
+import Combine
+import SwiftUI
+
+// MARK: - NetworkImageView
+
+struct NetworkImageView: View {
+    
+    // MARK: Internal
+    
+    init(url: URL?) {
+        
+        self.imageDownloader = .init(url: url)
+    }
+    
+    
+    // MARK: View
+    
+    var body: some View {
+        if let image = self.imageDownloader.image {
+            
+            Image(uiImage: image)
+                .resizable()
+                .aspectRatio(contentMode: .fit)
+        }
+        else {
+            
+            Circle()
+                .colorMultiply(Color(UIColor.placeholderText))
+                .onAppear {
+                
+                    self.imageDownloader.fetchImage()
+                }
+        }
+    }
+    
+    
+    // MARK: Private
+    
+    @ObservedObject
+    private var imageDownloader: ImageDownloader
+    
+    
+    // MARK: - NetworkImageView.ImageDownloader
+    
+    fileprivate final class ImageDownloader: ObservableObject {
+        
+        // MARK: FilePrivate
+        
+        private(set) var image: UIImage?
+        
+        let url: URL?
+        
+        init(url: URL?) {
+            
+            self.url = url
+            guard let url = url else {
+                
+                return
+            }
+            if let image = Self.cache[url] {
+                
+                self.image = image
+            }
+        }
+        
+        func fetchImage() {
+            
+            guard let url = url else {
+                
+                return
+            }
+            if let image = Self.cache[url] {
+                
+                self.objectWillChange.send()
+                self.image = image
+                return
+            }
+            self.cancellable = URLSession.shared
+                .dataTaskPublisher(for: url)
+                .receive(on: DispatchQueue.main)
+                .sink(
+                    receiveCompletion: { _ in },
+                    receiveValue: { output in
+                        
+                        if let image = UIImage(data: output.data) {
+                            
+                            Self.cache[url] = image
+                            self.objectWillChange.send()
+                            self.image = image
+                        }
+                    }
+                )
+        }
+        
+        
+        // MARK: Private
+        
+        private static var cache: [URL: UIImage] = [:]
+        
+        private var cancellable: AnyCancellable?
+    }
+}
+