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POGCD and cell reuse in UICollectionView
 

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  1. POGCD and cell reuse in UICollectionView
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    <p>I have a <code>UICollectionView</code> implementation with a custom <code>UICollectionViewCell</code>. The array of data is fetched from the internet but the images are downloaded as the user is accessing the content. </p> <p>While this is probably not the most efficient way and I do not plan on leave it this way, it did expose a certain issue which I am struggling to solve. It seems that the cells are displaying "cached" or "old" images and as I slowly scroll the collection view, the cell images keep on changing.</p> <p>This is probably an issue with the actual cell image not being available from the net at that moment in time and my question is how do I force an empty cell or some loading activitity monitor and not displaying an incorrect image?</p> <p>Thanks in advance, pinion</p> <pre><code>-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { static NSString * CellIdentifier = @"Event"; EventCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath]; NSString *title = [[events objectAtIndex:indexPath.item] objectForKey:@"title"]; NSString *imageUrl = [[[events objectAtIndex:indexPath.item] objectForKey:@"photo"] objectForKey:@"url"]; dispatch_queue_t imageFetchQ = dispatch_queue_create("image fetched", NULL); dispatch_async(imageFetchQ, ^{ NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]]; if (imageData) { dispatch_async(dispatch_get_main_queue(), ^{ cell.eventImage.image = [UIImage imageWithData:imageData]; cell.eventTitle.text = title; }); } }); return cell; } </code></pre>
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    1. USetolstoy
    1. USPinion
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      1. VTUpMod
    1. COI would advice you to use NSOperationQueue instead, something like in this tutorial: http://www.raywenderlich.com/19788/how-to-use-nsoperations-and-nsoperationqueues
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      1. POGCD and cell reuse in UICollectionView
      1. USOladya Kane
    2. COI tried following the tutorial but it doesn't really deal with the reuse issues. I see where NSOperationQueue will fit into such a solution but the problem remains the same. I think i need to implement some type of a mechanism to verify which image is about to be displayed per cell. not sure how though. yet.
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      1. POGCD and cell reuse in UICollectionView
      1. USPinion
 

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