Fix NSURLResponse not cached when SDWebImageDownloaderEnableNSURLCache is passed SDWebImage#326

Author: Olivier Poitrey

SDWebImage/SDWebImageDownloader.m

@@ -119,7 +119,7 @@ - (NSInteger)maxConcurrentDownloads
 
     [self addProgressCallback:progressBlock andCompletedBlock:completedBlock forURL:url createCallback:^
     {
-        // In order to prevent from potential duplicate caching (NSURLCache + SDImageCache) we disable the cache for image requests
+        // In order to prevent from potential duplicate caching (NSURLCache + SDImageCache) we disable the cache for image requests if told otherwise
         NSMutableURLRequest *request = [NSMutableURLRequest.alloc initWithURL:url cachePolicy:(options & SDWebImageDownloaderEnableNSURLCache ? NSURLRequestUseProtocolCachePolicy : NSURLRequestReloadIgnoringLocalCacheData) timeoutInterval:15];
         request.HTTPShouldHandleCookies = NO;
         request.HTTPShouldUsePipelining = YES;

SDWebImage/SDWebImageDownloaderOperation.m

@@ -311,8 +311,15 @@ - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)err
 
 - (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse
 {
-    // Prevents caching of responses
-    return nil;
+    if (self.request.cachePolicy == NSURLRequestReloadIgnoringLocalCacheData)
+    {
+        // Prevents caching of responses
+        return nil;
+    }
+    else
+    {
+        return cachedResponse;
+    }
 }