What is the proper way to use NSCache with dispatch_async in a reusable table cell?

Question

I have been looking for a clear cut way to do this and have not found anywhere that will give an example and explain it very well. I hope you can help me out.

Here i

Answer 1

Might be you did some wrong you setting same Key for each image of NSCache

[cache setValue:[UIImage imageWithData:imageData] forKey:@"image"];

Use this Instead of above set ForKey as a Imagepath item.image and use setObject instead of setVlaue:-

[self.imageCache setObject:image forKey:item.image];

try with this Code example:-

in .h Class:-

@property (nonatomic, strong) NSCache *imageCache;

in .m class:-

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.imageCache = [[NSCache alloc] init];

    // the rest of your viewDidLoad
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

     static NSString *cellIdentifier = @"cell";
     NewsCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];

     NewsItem *item = [newsItemsArray objectAtIndex:indexPath.row];
     cell.newsTitle.text = item.title;

    UIImage *cachedImage =   [self.imageCache objectForKey:item.image];;
    if (cachedImage)
    {
        cell.imageView.image = cachedImage;
    }
    else
    {
        cell.imageView.image = [UIImage imageNamed:@"blankthumbnail.png"];

        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

               NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:item.image]];
               UIImage *image    = nil;
                if (imageData) 
                     image = [UIImage imageWithData:imageData];

                if (image)
                {

                     [self.imageCache setObject:image forKey:item.image];
                }
              dispatch_async(dispatch_get_main_queue(), ^{
                        UITableViewCell *updateCell = [tableView cellForRowAtIndexPath:indexPath];
                        if (updateCell)
                           cell.imageView.image = [UIImage imageWithData:imageData];
                           NSLog(@"Record String = %@",[cache objectForKey:@"image"]);
                  });
          });            
    }
    return cell;
}