Disk-only cache writing and ability to flush memory cache

SAMCache/SAMCache.h

@@ -6,7 +6,7 @@
 //  Copyright (c) 2011-2014 Sam Soffes. All rights reserved.
 //
 
-#import <Foundation/Foundation.h>
+@import Foundation;
 
 @interface SAMCache : NSObject
 
@@ -105,14 +105,38 @@
 ///----------------------------------------
 
 /**
- Synchronously set an object in the cache for a given key.
+ Synchronously set an object in the memory cache for a given key, while asynchronously writing to the disk cache. Uses both memory and disk cache.
 
  @param object The object to store in the cache.
 
  @param key The key of the object.
  */
 - (void)setObject:(id <NSCoding>)object forKey:(NSString *)key;
 
+/**
+ Synchronously set an object in the memory cache for a given key, while asynchronously writing to the disk cache. Has an option to only write asynchronously to the disk cache.
+
+ @param object The object to store in the cache.
+
+ @param key The key of the object.
+
+ @param useDiskCacheOnly A value indicating whether or not to store the object in memory or only write object to disk cache location in an asynchronous fashion.
+ */
+- (void)setObject:(id <NSCoding>)object forKey:(NSString *)key diskCacheOnly:(BOOL)useDiskCacheOnly;
+
+/**
+ Synchronously set an object in the memory cache for a given key, while asynchronously writing to the disk cache. Has an option to only write asynchronously to the disk cache, along with a completion block for the asynchronous write operation.
+
+ @param object The object to store in the cache.
+
+ @param key The key of the object.
+
+ @param useDiskCacheOnly A value indicating whether or not to store the object in memory or only write object to disk cache location in an asynchronous fashion.
+
+ @param completionBlock A callback block that indicates that all operations (synchronous and asynchronous) have been completed, with an indication of success for the disk wrigin operation.
+ */
+- (void)setObject:(id <NSCoding>)object forKey:(NSString *)key diskCacheOnly:(BOOL)useDiskCacheOnly withCompletion:(void (^)(BOOL didSave))completionBlock;
+
 /**
  Remove an object from the cache.
 
@@ -125,6 +149,11 @@
  */
 - (void)removeAllObjects;
 
+/**
+ Removes all cached objects from the memory cache. Does not remove disk-cache
+ entries.
+ */
+- (void)flushMemoryCache;
 
 ///-------------------------------
 /// @name Accessing the Disk Cache
@@ -171,7 +200,7 @@
 
 #if TARGET_OS_IPHONE
 
-#import <UIKit/UIImage.h>
+@import UIKit.UIImage;
 
 @interface SAMCache (UIImageAdditions)
 
@@ -203,14 +232,25 @@
 - (void)imageForKey:(NSString *)key usingBlock:(void (^)(UIImage *image))block;
 
 /**
- Synchronously store a PNG representation of an image in the cache for a given key.
+ Synchronously store a PNG representation of an image in the cache for a given key. Uses both memory and disk cache.
 
  @param image The image to store in the cache.
 
  @param key The key of the image.
  */
 - (void)setImage:(UIImage *)image forKey:(NSString *)key;
 
+/**
+ Synchronously store a PNG representation of an image in the cache for a given key.
+
+ @param image The image to store in the cache.
+
+ @param key The key of the image.
+
+ @param useDiskCacheOnly A value indicating whether or not to store the object in memory or only write object to disk cache location.
+ */
+- (void)setImage:(UIImage *)image forKey:(NSString *)key diskCacheOnly:(BOOL)useDiskCacheOnly;
+
 /**
  Synchronously check if an image exists in the cache without retriving it.
 

SAMCache/SAMCache.m

@@ -166,24 +166,41 @@ - (BOOL)objectExistsForKey:(NSString *)key {
 #pragma mark - Adding and Removing Cached Values
 
 - (void)setObject:(id <NSCoding>)object forKey:(NSString *)key {
-	NSParameterAssert(key);
+	[self setObject:object forKey:key diskCacheOnly:NO];
+}
+
+- (void)setObject:(id <NSCoding>)object forKey:(NSString *)key diskCacheOnly:(BOOL)useDiskCacheOnly {
+    [self setObject:object forKey:key diskCacheOnly:useDiskCacheOnly withCompletion:nil];
+}
 
+- (void)setObject:(id <NSCoding>)object forKey:(NSString *)key diskCacheOnly:(BOOL)useDiskCacheOnly withCompletion:(void (^)(BOOL didSave))completionBlock {
+    NSParameterAssert(key);
+
 	// If there's no object, delete the key.
 	if (!object) {
 		[self removeObjectForKey:key];
 		return;
 	}
-
-	// Save to memory cache
-	[self.cache setObject:object forKey:key];
-
+
+    if (useDiskCacheOnly == NO) {
+        // Save to memory cache
+        [self.cache setObject:object forKey:key];
+    }
+
+    __weak SAMCache *weakSelf = self;
+
 	dispatch_async(self.diskQueue, ^{
+        __strong SAMCache *strongSelf = weakSelf;
+
 		// Save to disk cache
-		[NSKeyedArchiver archiveRootObject:object toFile:[self _pathForKey:key]];
+		BOOL didSave = [NSKeyedArchiver archiveRootObject:object toFile:[strongSelf _pathForKey:key]];
+
+        if (completionBlock) {
+            completionBlock(didSave);
+        }
 	});
 }
 
-
 - (void)removeObjectForKey:(NSString *)key {
 	NSParameterAssert(key);
 
@@ -202,10 +219,12 @@ - (void)removeAllObjects {
 		for (NSString *path in [self.fileManager contentsOfDirectoryAtPath:self.directory error:nil]) {
 			[self.fileManager removeItemAtPath:[self.directory stringByAppendingPathComponent:path] error:nil];
 		}
-		[self.fileManager removeItemAtPath:self.directory error:nil];
 	});
 }
 
+- (void)flushMemoryCache {
+    [self.cache removeAllObjects];
+}
 
 #pragma mark - Accessing the Disk Cache
 
@@ -262,7 +281,7 @@ - (NSString *)_pathForKey:(NSString *)key {
 
 #if TARGET_OS_IPHONE
 
-#import <UIKit/UIScreen.h>
+@import UIKit.UIScreen;
 
 @implementation SAMCache (UIImageAdditions)
 
@@ -319,28 +338,33 @@ - (void)imageForKey:(NSString *)key usingBlock:(void (^)(UIImage *image))block {
 
 
 - (void)setImage:(UIImage *)image forKey:(NSString *)key {
-	NSParameterAssert(key);
+	[self setImage:image forKey:key diskCacheOnly:NO];
+}
 
+- (void)setImage:(UIImage *)image forKey:(NSString *)key diskCacheOnly:(BOOL)useDiskCacheOnly {
+    NSParameterAssert(key);
+
 	// If there's no image, delete the key.
 	if (!image) {
 		[self removeObjectForKey:key];
 		return;
 	}
-
+    
 	key = [[self class] _keyForImageKey:key];
-
+    
 	dispatch_async(self.diskQueue, ^{
 		NSString *path = [self _pathForKey:key];
-
-		// Save to memory cache
-		[self.cache setObject:image forKey:key];
-
+
+        if (useDiskCacheOnly == NO) {
+            // Save to memory cache
+            [self.cache setObject:image forKey:key];
+        }
+
 		// Save to disk cache
 		[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];
 	});
 }
 
-
 - (BOOL)imageExistsForKey:(NSString *)key {
 	NSParameterAssert(key);
 	return [self objectExistsForKey:[[self class] _keyForImageKey:key]];

Tests/SAMCacheTests.m

@@ -69,4 +69,40 @@ - (void)testReadingWithSubscript {
 	XCTAssertEqualObjects(@"subread", self.cache[@"subscriptRead"], @"Reading an object with a subscript");
 }
 
+- (void)testAddingToDiskCacheOnly {
+    [self.cache setObject:@42 forKey:@"answer" diskCacheOnly:YES];
+
+    XCTAssertNil([self.cache.cache objectForKey:@"answer"]);
+
+    XCTAssertEqualObjects(@42, [self.cache objectForKey:@"answer"], @"Reading from disk cache");
+
+    XCTAssertNotNil([self.cache.cache objectForKey:@"answer"]);
+}
+
+- (void)testAddingToDiskCacheOnlyWithCallback {
+    XCTestExpectation *diskWriteExpectation = [self expectationWithDescription:@"object written to disk"];
+
+    __weak SAMCacheTests *weakSelf = self;
+
+    [weakSelf.cache setObject:@42 forKey:@"answer" diskCacheOnly:YES withCompletion:^(BOOL didSave) {
+        XCTAssert(didSave);
+        [diskWriteExpectation fulfill];
+    }];
+
+    [self waitForExpectationsWithTimeout:1 handler:nil];
+}
+
+- (void)testFlushMemoryCache {
+    [self.cache setObject:@42 forKey:@"answer"];
+    XCTAssertEqualObjects(@42, [self.cache objectForKey:@"answer"], @"Reading from memory cache");
+
+    [self.cache flushMemoryCache];
+
+    XCTAssertNil([self.cache.cache objectForKey:@"answer"]);
+
+    XCTAssertEqualObjects(@42, [self.cache objectForKey:@"answer"], @"Reading from disk cache");
+
+    XCTAssertNotNil([self.cache.cache objectForKey:@"answer"]);
+}
+
 @end