feat(): implemented custom cache and custom cache key

Author: Christian Elies

Sources/RemoteImage/private/Services/DefaultRemoteImageCache.swift

@@ -0,0 +1,18 @@
+//
+//  DefaultRemoteImageCache.swift
+//  
+//
+//  Created by Christian Elies on 14.12.19.
+//
+
+import Foundation
+
+struct DefaultRemoteImageCache {
+    let cache = NSCache<AnyObject, PlatformSpecificImageType>()
+}
+
+extension DefaultRemoteImageCache: RemoteImageCache {
+    func object(forKey key: AnyObject) -> PlatformSpecificImageType? { cache.object(forKey: key) }
+
+    func setObject(_ object: PlatformSpecificImageType, forKey key: AnyObject) { cache.setObject(object, forKey: key) }
+}

Sources/RemoteImage/public/Protocols/RemoteImageCache.swift

@@ -0,0 +1,13 @@
+//
+//  RemoteImageCache.swift
+//  
+//
+//  Created by Christian Elies on 14.12.19.
+//
+
+import Foundation
+
+public protocol RemoteImageCache {
+    func object(forKey key: AnyObject) -> PlatformSpecificImageType?
+    func setObject(_ object: PlatformSpecificImageType, forKey key: AnyObject)
+}

Sources/RemoteImage/public/Services/RemoteImageService.swift

@@ -10,17 +10,25 @@ import Combine
 import Foundation
 
 public final class RemoteImageService: NSObject, ObservableObject {
+    public typealias RemoteImageCacheKeyProvider = (RemoteImageType) -> AnyObject
+
     private let dependencies: RemoteImageServiceDependenciesProtocol
     private var cancellable: AnyCancellable?
-    
+
     @Published var state: RemoteImageState = .loading
-    
-    public static let cache = NSCache<NSObject, PlatformSpecificImageType>()
-    
+
+    public static var cache: RemoteImageCache = DefaultRemoteImageCache()
+    public static var cacheKeyProvider: RemoteImageCacheKeyProvider = { remoteImageType in
+        switch remoteImageType {
+        case .phAsset(let localIdentifier): return localIdentifier as NSString
+        case .url(let url): return url as NSURL
+        }
+    }
+
     init(dependencies: RemoteImageServiceDependenciesProtocol) {
         self.dependencies = dependencies
     }
-    
+
     func fetchImage(ofType type: RemoteImageType) {
         switch type {
         case .url(let url):
@@ -34,15 +42,16 @@ public final class RemoteImageService: NSObject, ObservableObject {
 extension RemoteImageService {
     private func fetchImage(atURL url: URL) {
         cancellable?.cancel()
-        
-        if let image = RemoteImageService.cache.object(forKey: url as NSURL) {
+
+        let cacheKey = Self.cacheKeyProvider(.url(url))
+        if let image = Self.cache.object(forKey: cacheKey) {
             state = .image(image)
             return
         }
-        
+
         let urlSession = URLSession.shared
         let urlRequest = URLRequest(url: url)
-        
+
         cancellable = urlSession.dataTaskPublisher(for: urlRequest)
             .map { PlatformSpecificImageType(data: $0.data) }
             .receive(on: RunLoop.main)
@@ -54,23 +63,24 @@ extension RemoteImageService {
                 }
             }) { image in
                 if let image = image {
-                    RemoteImageService.cache.setObject(image, forKey: url as NSURL)
+                    Self.cache.setObject(image, forKey: cacheKey)
                     self.state = .image(image)
                 } else {
                     self.state = .error(RemoteImageServiceError.couldNotCreateImage)
                 }
             }
     }
-    
+
     private func fetchImage(withLocalIdentifier localIdentifier: String) {
-        if let image = RemoteImageService.cache.object(forKey: localIdentifier as NSString) {
+        let cacheKey = Self.cacheKeyProvider(.phAsset(localIdentifier: localIdentifier))
+        if let image = Self.cache.object(forKey: cacheKey) {
             state = .image(image)
             return
         }
-        
+
         dependencies.photoKitService.getPhotoData(localIdentifier: localIdentifier, success: { data in
             if let image = PlatformSpecificImageType(data: data) {
-                RemoteImageService.cache.setObject(image, forKey: localIdentifier as NSString)
+                Self.cache.setObject(image, forKey: cacheKey)
                 self.state = .image(image)
             } else {
                 self.state = .error(RemoteImageServiceError.couldNotCreateImage)