Synchronous NSURL request can't cache

[blueFLoyd8]

My app loads a large number of images from the server and displays them. I am using an operation queue to do the loading and a synchronous request within the operation to get the image (because asynchronous is not allowed apparently within an operation).

I am running into a cache problem. None of URL responses are getting cached and I do not know how to fix it. here is the code from my operation:

.h

@interface DRGetImageOperation : NSOperation {
	NSURL *objectURL;
	NSNumber *index;
	UIViewController *mainViewController;
	SEL callback;
}
@property (nonatomic, retain) NSURL *objectURL;
- (id)initWithViewController:(UIViewController *)viewController andIndex:(int)number;
- (void) setCallback:(SEL)select;
@end

.m

// Partial code. Some small methods are not shown
- (void)main {
	NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
	NSLog(@"URL = %@", objectURL);
	NSLog(@"Cache size before = %d bytes", [[NSURLCache sharedURLCache] currentMemoryUsage]);
	NSData *data = nil;
	NSHTTPURLResponse *response = NULL;
	NSError *error = nil;
	NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:objectURL cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:20];
	data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
	NSLog(@"Image Request finished. Error = %@",[error localizedDescription]);
	NSLog(@"Cache size after = %d bytes", [[NSURLCache sharedURLCache] currentMemoryUsage]);
        // Cache size = 0 ALWAYS!
    if (error == nil) {
		UIImage *photo = [UIImage imageWithData:data];
		if (photo) {
			[mainViewController performSelectorOnMainThread:callback
												 withObject:[NSArray arrayWithObjects:photo, index, nil] 
											  waitUntilDone:YES];
			[pool release];
			return;	
		}
		
	}
	// ELSE (Error happened)
	[mainViewController performSelectorOnMainThread:callback
										 withObject:[NSArray arrayWithObjects:nil] 
									  waitUntilDone:YES];
	[pool release];
}