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POCacheing UIImage as NSData and getting it back
 

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    <p>I'm trying to cache images I load from Flickr. If I load the same image, I'm hoping to use the cached version instead. For some reason, when I download an image from the internet, it works, but if I load it from my cache, it displays a blank image. I checked cacheData, and it has the same amount of bits as the image I put in, so it appears loading the file is working. </p> <p>Here is how I cache images:</p> <pre><code>+ (void)cachePhoto:(NSData *)photo withKey:(NSString *)key { if (photo) { NSArray * urlArray = [fileManager URLsForDirectory:NSCachesDirectory inDomains:NSUserDomainMask]; NSURL * targetDirectory = (NSURL *)[urlArray objectAtIndex:0]; targetDirectory = [targetDirectory URLByAppendingPathComponent:key]; [photo writeToURL:targetDirectory atomically:YES]; [cachedPhotos addObject:key]; NSLog(@"target url %@", targetDirectory); } } + (NSData *)photoInCache:(NSString *)key { if ([cachedPhotos containsObject:key]) { NSString * path = [[cacheDirectory URLByAppendingPathComponent:key] path]; NSLog(@"path: %@", path); return [fileManager contentsAtPath:path]; } else { return nil; } } </code></pre> <p>And my code to get it back:</p> <pre><code>NSData * cacheData = [PhotoCache photoInCache:key]; if (cacheData) { self.imageView.image = [UIImage imageWithData:cacheData]; [spinner stopAnimating]; NSLog(@"used cached image"); } else { dispatch_queue_t downloadQueue = dispatch_queue_create("get photo from flickr", NULL); dispatch_async(downloadQueue, ^{ NSData * imageData = [[NSData alloc] initWithContentsOfURL:url]; dispatch_async(dispatch_get_main_queue(), ^{ [spinner stopAnimating]; self.imageView.image = [UIImage imageWithData:imageData]; [PhotoCache cachePhoto:imageData withKey:key]; }); }); } </code></pre>
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    1. CONSData *thumbnailData = UIImagePNGRepresentation(thumbnailImage); try this line of code.
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