Merge pull request #498 from donholly/master

Added and exposed some methods that allow to check if an image exists on...

SDWebImage/SDImageCache.h

@@ -159,4 +159,9 @@ typedef enum SDImageCacheType SDImageCacheType;
  */
 - (void)calculateSizeWithCompletionBlock:(void (^)(NSUInteger fileCount, unsigned long long totalSize))completionBlock;
 
+/**
+ * Check if image exists in cache already
+ */
+- (BOOL)diskImageExistsWithKey:(NSString *)key;
+
 @end

SDWebImage/SDImageCache.m

@@ -25,7 +25,9 @@ static const NSInteger kDefaultCacheMaxCacheAge = 60 * 60 * 24 * 7; // 1 week
 @end
 
 
-@implementation SDImageCache
+@implementation SDImageCache {
+    NSFileManager *_fileManager;
+}
 
 + (SDImageCache *)sharedImageCache
 {
@@ -60,6 +62,11 @@ static const NSInteger kDefaultCacheMaxCacheAge = 60 * 60 * 24 * 7; // 1 week
         NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
         _diskCachePath = [paths[0] stringByAppendingPathComponent:fullNamespace];
 
+        dispatch_sync(_ioQueue, ^
+        {
+            _fileManager = NSFileManager.new;
+        });
+        
 #if TARGET_OS_IPHONE
         // Subscribe to app events
         [[NSNotificationCenter defaultCenter] addObserver:self
@@ -184,6 +191,17 @@ static const NSInteger kDefaultCacheMaxCacheAge = 60 * 60 * 24 * 7; // 1 week
     [self storeImage:image imageData:nil forKey:key toDisk:toDisk];
 }
 
+- (BOOL)diskImageExistsWithKey:(NSString *)key
+{
+    __block BOOL exists = NO;
+    dispatch_sync(_ioQueue, ^
+    {
+        exists = [_fileManager fileExistsAtPath:[self defaultCachePathForKey:key]];
+    });
+    
+    return exists;
+}
+
 - (UIImage *)imageFromMemoryCacheForKey:(NSString *)key
 {
     return [self.memCache objectForKey:key];

SDWebImage/SDWebImageManager.h

@@ -171,4 +171,9 @@ SDWebImageManager *manager = [SDWebImageManager sharedManager];
  */
 - (BOOL)isRunning;
 
+/**
+ * Check if image has already been cached
+ */
+- (BOOL)diskImageExistsForURL:(NSURL *)url;
+
 @end

SDWebImage/SDWebImageManager.m

@@ -66,6 +66,12 @@
     }
 }
 
+- (BOOL)diskImageExistsForURL:(NSURL *)url
+{
+    NSString *key = [self cacheKeyForURL:url];
+    return [self.imageCache diskImageExistsWithKey:key];
+}
+
 - (id<SDWebImageOperation>)downloadWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletedWithFinishedBlock)completedBlock
 {    
     // Invoking this method without a completedBlock is pointless