I'm pretty new to Objective-C so hopefully this all makes sense. I've downloaded images from a server and have displayed them in an image view in the collectionView cellForItemAtIndexPath:
method. The issue I'm facing is that the images don't appear to be caching. It looks like each time a cell is being reused, the associated image from the server is being re-downloaded.
In my viewDidLoad method I'm creating a NSMutableDictionary:
imageDictionary = [[NSMutableDictionary alloc]initWithCapacity:50.0];
From reading the documentation and looking at answers to similar questions I thought that this, plus the following code would be enough. I've been at this for a couple of days and I know there is something I'm missing or a concept I'm not grasping.
#pragma mark - UICollectionView Data Source
- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section;{
NSLog(@"Begin retrieving photos");
return [self.photos count];
}
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
return 1;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath;{
CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MY_CELL" forIndexPath:indexPath];
cell.imageView.image = nil;
if (cell.imageView.image == nil) {
dispatch_queue_t downloadQueue = dispatch_queue_create("image downloader", NULL);
dispatch_async(downloadQueue, ^{
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[self.photos objectAtIndex:indexPath.row] objectForKey:@"fullimage"]]];
UIImage *image = [UIImage imageWithData:data];
[imageDictionary setObject:image forKey:@"Image"];
dispatch_async(dispatch_get_main_queue(), ^{
cell.imageView.image = [imageDictionary objectForKey:@"Image"];
[cell setNeedsDisplay];
});
});
}
return cell;
}
Any help would be greatly appreciated. Thanks in advance.
@yuf - thanks again for the direction. NSCache seems to be getting me the results I was after. Here is the code that is working properly. If anyone has a similar issue, you can compare the following to my original question.