- added two helper methods for directory managing

TWRDownloadManager.h

@@ -59,6 +59,8 @@
 - (void)cancelAllDownloads;
 - (void)cancelDownloadForUrl:(NSString *)fileIdentifier;
 
+- (void)cleanDirectoryNamed:(NSString *)directory;
+
 - (BOOL)isFileDownloadingForUrl:(NSString *)url withProgressBlock:(void(^)(CGFloat progress))block;
 - (BOOL)isFileDownloadingForUrl:(NSString *)url withProgressBlock:(void(^)(CGFloat progress))block completionBlock:(void(^)(BOOL completed))completionBlock;
 

TWRDownloadManager.m

@@ -222,6 +222,7 @@ - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTas
     TWRDownloadObject *download = [self.downloads objectForKey:fileIdentifier];
 
     if (download.directoryName) {
+        [self createDirectoryNamed:download.directoryName];
         destinationLocation = [[[self cachesDirectoryUrlPath] URLByAppendingPathComponent:download.directoryName] URLByAppendingPathComponent:download.fileName];
     } else {
         destinationLocation = [[self cachesDirectoryUrlPath] URLByAppendingPathComponent:download.fileName];
@@ -258,6 +259,18 @@ - (CGFloat)remainingTimeForDownload:(TWRDownloadObject *)download
 
 #pragma mark - File Management
 
+- (BOOL)createDirectoryNamed:(NSString *)directory {
+    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
+    NSString *cachesDirectory = [paths objectAtIndex:0];
+    NSString *targetDirectory = [cachesDirectory stringByAppendingPathComponent:directory];
+
+    NSError *error;
+    return [[NSFileManager defaultManager] createDirectoryAtPath:targetDirectory
+                                     withIntermediateDirectories:YES
+                                                      attributes:nil
+                                                           error:&error];
+}
+
 - (NSURL *)cachesDirectoryUrlPath {
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
     NSString *cachesDirectory = [paths objectAtIndex:0];
@@ -375,7 +388,15 @@ - (BOOL)deleteFileWithName:(NSString *)fileName
     return deleted;
 }
 
-#pragma mark - Clean tmp directory
+#pragma mark - Clean directory
+
+- (void)cleanDirectoryNamed:(NSString *)directory {
+    NSFileManager *fm = [NSFileManager defaultManager];
+    NSError *error = nil;
+    for (NSString *file in [fm contentsOfDirectoryAtPath:directory error:&error]) {
+        [fm removeItemAtPath:[directory stringByAppendingPathComponent:file] error:&error];
+    }
+}
 
 - (void)cleanTmpDirectory {
     NSArray* tmpDirectory = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:NSTemporaryDirectory() error:NULL];
@@ -386,7 +407,7 @@ - (void)cleanTmpDirectory {
 
 #pragma mark - Background download
 
--(void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session {
+- (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session {
     // Check if all download tasks have been finished.
     [session getTasksWithCompletionHandler:^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) {
         if ([downloadTasks count] == 0) {