If cache not found in-memory, but found on disk, will set in-memory f…

…rom disk before returning cache

Source/Shared/BasicHybridCache.swift

@@ -32,16 +32,22 @@ public class BasicHybridCache: NSObject {
    - Parameter name: A name of the cache
    - Parameter config: Cache configuration
    */
-  public init(name: String, config: Config = Config.defaultConfig) {
+  public convenience init(name: String, config: Config = Config.defaultConfig) {
+    let frontStorage = StorageFactory.resolve(name, kind: config.frontKind, maxSize: UInt(config.maxObjects))
+    let backStorage = StorageFactory.resolve(name, kind: config.backKind, maxSize: config.maxSize)
+    self.init(name: name, frontStorage: frontStorage, backStorage: backStorage, config: config)
+
+  }
+  internal init(name: String, frontStorage: StorageAware, backStorage: StorageAware, config: Config) {
     self.name = name
+    self.frontStorage = frontStorage
+    self.backStorage = backStorage
     self.config = config
 
-    frontStorage = StorageFactory.resolve(name, kind: config.frontKind, maxSize: UInt(config.maxObjects))
-    backStorage = StorageFactory.resolve(name, kind: config.backKind, maxSize: config.maxSize)
     super.init()
-
+    
     let notificationCenter = NotificationCenter.default
-
+    
     #if os(macOS)
       notificationCenter.addObserver(self, selector: #selector(clearExpiredDataInBackStorage),
                                      name: NSNotification.Name.NSApplicationWillTerminate, object: nil)
@@ -56,7 +62,7 @@ public class BasicHybridCache: NSObject {
                                      name: .UIApplicationDidEnterBackground, object: nil)
     #endif
   }
-
+  
   /**
    Removes notification center observer.
    */
@@ -109,10 +115,26 @@ public class BasicHybridCache: NSObject {
       }
 
       weakSelf.backStorage.object(key) { (object: T?) in
-        completion(object)
+        guard let object = object else {
+            completion(nil)
+            return
+        }
+        weakSelf.copyToFrontStorage(key, object: object, completion: completion)
       }
     }
   }
+
+  private func copyToFrontStorage<T: Cachable>(_ key: String, object: T, completion: @escaping (_ object: T?) -> Void) {
+    self.backStorage.objectMetadata(key) { [weak self] (metadata: ObjectMetadata?) in
+      guard let weakSelf = self, let metadata = metadata else {
+        completion(nil)
+        return
+      }
+      weakSelf.frontStorage.add(key, object: object, expiry: metadata.expiry, completion: { _ in
+        completion(object)
+      })
+    }
+  }
 
   /**
    Removes the object from to the front and back cache storages.

Source/Shared/Storage/DiskStorage.swift

@@ -81,6 +81,30 @@ public final class DiskStorage: StorageAware {
       completion?()
     }
   }
+
+  /**
+   Gets information about the cached object.
+   
+   - Parameter key: Unique key to identify the object in the cache
+   - Parameter completion: Completion closure returns object metadata
+   */
+  public func objectMetadata(_ key: String, completion: @escaping (_ metadata: ObjectMetadata?) -> Void) {
+    readQueue.async { [weak self] in
+      guard let weakSelf = self else {
+        completion(nil)
+        return
+      }
+
+      do {
+        let attributes = try weakSelf.fileManager.attributesOfItem(atPath: weakSelf.filePath(key))
+        let fileModifiedDate = Expiry.date(attributes[FileAttributeKey.modificationDate] as! Date)
+        completion(ObjectMetadata(expiry: fileModifiedDate))
+
+      } catch {
+        completion(nil)
+      }
+    }
+  }
 
   /**
    Tries to retrieve the object from the disk storage.

Source/Shared/Storage/MemoryStorage.swift

@@ -65,6 +65,29 @@ public final class MemoryStorage: StorageAware {
     }
   }
 
+  /**
+   Gets information about the cached object.
+   
+   - Parameter key: Unique key to identify the object in the cache
+   - Parameter completion: Completion closure returns object metadata
+   */
+  public func objectMetadata(_ key: String, completion: @escaping (_ metadata: ObjectMetadata?) -> Void) {
+    readQueue.async { [weak self] in
+      guard let weakSelf = self else {
+        completion(nil)
+        return
+      }
+
+      guard let capsule = weakSelf.cache.object(forKey: key as AnyObject) as? Capsule else {
+        completion(nil)
+        return
+      }
+
+      let expiryDate = Expiry.date(capsule.expiryDate)
+      completion(ObjectMetadata(expiry: expiryDate))
+    }
+  }
+
   /**
    Tries to retrieve the object from the memory storage.
 

Tests/iOS/Specs/CacheSpec.swift

@@ -80,6 +80,34 @@ class CacheSpec: QuickSpec {
 
           self.waitForExpectations(timeout: 4.0, handler:nil)
         }
+
+        it("should resolve from disk and set in-memory cache if object not in-memory") {
+            let frontStorage = MemoryStorage(name: "MemoryStorage")
+            let backStorage = DiskStorage(name: "DiskStorage")
+            let config = Config.defaultConfig
+            let key = "myusernamedjohn"
+            let object = SpecHelper.user
+
+            let cache = Cache<User>(name: "MyCache", frontStorage: frontStorage, backStorage: backStorage, config: config)
+
+            waitUntil(timeout: 4.0) { done in
+
+                backStorage.add(key, object: object) {
+
+                    cache.object(key) { (receivedObject: User?) in
+
+                        expect(receivedObject?.firstName).to(equal(object.firstName))
+                        expect(receivedObject?.lastName).to(equal(object.lastName))
+
+                        frontStorage.object(key) { (inmemoryCachedUser: User?) in
+                            expect(inmemoryCachedUser?.firstName).to(equal(object.firstName))
+                            expect(inmemoryCachedUser?.lastName).to(equal(object.lastName))
+                            done()
+                        }
+                    }
+                }
+            }
+        }
       }
 
       describe("#remove") {