NSOperation problem

Question

I'm trying to load images from url's and place one image per row in my tableview. Here's the code that I have so far which comes close to working, but not quite. The problem is that the images in the table rows keep updating to the latest one downloaded. Once the image in row 0 has been set, it shouldn't change when the image is downloaded for row 1. I can't count on knowing beforehand how many rows and images I'm going to handle.
Thanks.
-Phil
.h
@interface OSCouponsVC : UIViewController <ADBannerViewDelegate,
CLLocationManagerDelegate,
UITableViewDelegate,
UITableViewDataSource>
IBOutlet UITableView* couponsTableView;
NSData* coasterData;
IBOutlet UITableViewCell* dynCell;
NSArray* coupons;
@property (nonatomic, retain) UITableView* couponsTableView;
@property (nonatomic, retain) NSData* coasterData;
@property (nonatomic, retain) UITableViewCell* dynCell;
@property (nonatomic, retain) NSArray* coupons;
@end
.m
- (void)viewDidLoad {
[super viewDidLoad];
self.couponsTableView.delegate = self;
self.couponsTableView.dataSource = self;
self.coasterData = [[NSData alloc] init];
- (void)loadCoasterData:(NSURL*)url {
NSOperationQueue* queue = [[NSOperationQueue alloc] init];
NSInvocationOperation* operation = [[NSInvocationOperation alloc] initWithTarget:self
selector:@selector(loadDataWithOperation:)
object:url];
[queue addOperation:operation];
[operation release];
- (void)loadDataWithOperation:(NSURL*)url {
NSData* imageData = [NSData dataWithContentsOfURL:url];
self.coasterData = imageData;
[self.couponsTableView performSelectorOnMainThread:@selector(reloadData)
withObject:nil
waitUntilDone:YES];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString* myID = @"CouponsCellID";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:myID];
if (cell == nil) {
[[NSBundle mainBundle] loadNibNamed:@"CouponsDynCell" owner:self options:nil];
cell = self.dynCell;
self.dynCell = nil;
UIImageView* tempImageView;
//// COASTER ////
tempImageView = (UIImageView*)[cell viewWithTag:1];
NSURL* theURL = [NSURL URLWithString:[[self.coupons objectAtIndex:(couponCategory * 3) + indexPath.row] objectForKey:@"coaster_url"]];
[self loadCoasterData:theURL];
tempImageView.image = [UIImage imageWithData:self.coasterData];
return cell;

Answer 1

Another code example - here the main thread actually counts to 1000 first, then the op1, and then op2. This can of course be a coincidence, but I've run it a few times
require 'osx/cocoa'
include OSX
class MyOp < NSOperation
def main
i = 0
(1..1000).each{|i| puts "Ping #{i} from op #{self.inspect}"}
end
end
class AppDelegate < NSObject
def applicationDidFinishLaunching(aNotification)
queue = NSOperationQueue.new
queue.addOperation(MyOp.new)
queue.addOperation(MyOp.new)
(1..1000).each{|i| puts "Ping #{i} from app #{self.inspect}"}
end
end
NSApplication.sharedApplication
NSApp.setDelegate(AppDelegate.alloc.init)
NSApp.run