image on table after download

Question

I have tableview and image on cell. I have problem when try to return heightForRowAtIndexPath (image not the same height)

this's my class, it's will be crash when i'm try to scroll down. "2016-07-07 21:44:16.990 xem.vn[1725:25586] * Terminating app due to uncaught exception 'NSRangeException', reason: '* -[__NSArrayM objectAtIndex:]: index 2 beyond bounds [0 .. 1]'"

- (void)viewDidLoad {
    [listImage addObject:@"https://www.nasa.gov/sites/default/files/styles/image_card_4x3_ratio/public/thumbnails/image/leisa_christmas_false_color.png?itok=Jxf0IlS4"];
    [listImage addObject:@"https://pixabay.com/static/uploads/photo/2015/10/01/21/39/background-image-967820_960_720.jpg"];
    [listImage addObject:@"https://www.nasa.gov/sites/default/files/styles/image_card_4x3_ratio/public/thumbnails/image/idcs1426.jpg?itok=Gc_-Q58L"];
    [listImage addObject:@"https://www.nasa.gov/sites/default/files/styles/image_card_4x3_ratio/public/thumbnails/image/leisa_christmas_false_color.png?itok=Jxf0IlS4"];
    [listImage addObject:@"https://pixabay.com/static/uploads/photo/2015/10/01/21/39/background-image-967820_960_720.jpg"];
    [listImage addObject:@"https://www.nasa.gov/sites/default/files/styles/image_card_4x3_ratio/public/thumbnails/image/idcs1426.jpg?itok=Gc_-Q58L"];
    [listImage addObject:@"https://www.nasa.gov/sites/default/files/styles/image_card_4x3_ratio/public/thumbnails/image/leisa_christmas_false_color.png?itok=Jxf0IlS4"];
    [listImage addObject:@"https://pixabay.com/static/uploads/photo/2015/10/01/21/39/background-image-967820_960_720.jpg"];
    [listImage addObject:@"https://www.nasa.gov/sites/default/files/styles/image_card_4x3_ratio/public/thumbnails/image/idcs1426.jpg?itok=Gc_-Q58L"];
    imageHeights = [[NSMutableArray alloc]init];
    [self setDefaultRowHeights];
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    return [listImage count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
    static NSString *CellIdentifier = @"newTableViewCell";
    newTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = (newTableViewCell *)[[NSBundle mainBundle] loadNibNamed:CellIdentifier owner:self options:nil][0];
    }
    NSString *imageURL = listImage[indexPath.row];
    __weak newTableViewCell *weakCell = cell;
    __weak typeof(self) weakSelf = self;
    [cell.NewsImageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:imageURL]]
                              placeholderImage:[UIImage new]
                                       success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                                           weakCell.NewsImageView.image = image;
                                           NSInteger oldHeight = [imageHeights[indexPath.row] integerValue];
                                           NSInteger newHeight = (int)image.size.height;
                                           if (image.size.width != CGRectGetWidth(weakCell.NewsImageView.bounds)) {
                                               CGFloat ratio = image.size.height / image.size.width;
                                               newHeight = CGRectGetWidth(self.view.bounds) * ratio;
                                           }

                                           if (oldHeight != newHeight) {
                                               imageHeights[indexPath.row] = @(newHeight);
                                               [weakSelf.NewsTableView beginUpdates];
                                               [cell layoutIfNeeded];
                                               [weakSelf.NewsTableView endUpdates];
                                           }
                                       } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
                                           NSLog(@"Error: %@\nFetching image with url: %@", error, request.URL);
                                       }];
    return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return [imageHeights[indexPath.row] integerValue];
}
- (void)setDefaultRowHeights {
    imageHeights = [NSMutableArray arrayWithCapacity:listImage.count];
    for (int i = 0; i < listImage.count; i++) {
        imageHeights[i] = @(self.NewsTableView.rowHeight);
    }
}

thank for help!!

Answer 1

I believe the crash is due to your imageHeights and listImage having different number of item. After viewDidLoad is run, your listImage have 8 items but imageHeights 0 item even after running the setDefaultRowHeights.

The imageHeights = [NSMutableArray arrayWithCapacity:listImage.count] only say imageHeights will hold same count object as listImage, but the number of count in imageHeights is still 0.

I am unsure about if self.NewsTableView is setup correctly. Assuming that it is correct, the setDefaultRowHeights should be written like this:

- (void)setDefaultRowHeights {
    imageHeights = [NSMutableArray arrayWithCapacity:listImage.count];
    for (int i = 0; i < listImage.count; i++) {
      [imageHeights addObject:@(self.NewsTableView.rowHeight)];
    }
}