Cells are overlapping - ios

Question

I have a problem in my iPhone app. Sometimes, some cells of the UITableView of my home screen are overlapping and does not appear correctly.
Here is how sometimes (very rarely) my app is appearing :
I created two types of custom UITableViewCell, with a xib file to design them.
Do you have any idea on what can cause this ? Is this a bug of iOS, because I already noticed this kind of bug in an other app.
Thanks for your help.
UPDATE : here is my tableView:heightForRowAtIndexPath: method.
I'm returning the correct height depending on the two types of cells.
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
Article *article = [self.articles objectAtIndex:[indexPath row]];
if (article.isFeatured) {
return 110;
} else {
return 75;
}
}

Answer 1

Unless you are overriding -tableView:heightForRowAtIndexPath: with the height of your cell, all your cells will have the standard height of 44 points.
In your TableView Delegate you need to have
- (CGFloat)tableView:(UITableView *) tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
CGFloat cellHeight = 44.0;
//Calculate your cell height using indexPath and save it in cellHeight;
// Then
return cellHeight;
}

Answer 2

Try this
NSString *CellIdentifier = [NSString stringWithFormat:#"Cell %d",indexPath.row];
UITableViewCell *cell=[self.tableView cellForRowAtIndexPath:indexPath];
if (cell == nil)
{
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 30.0f;
}

Answer 3

I think you to calculate your cell height dynamically according to you content.
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
CGSize constrainedSize = CGSizeMake(self.view.frame.size.width - 30, FLT_MAX);
NSDictionary *attributesDictionary = [NSDictionary dictionaryWithObjectsAndKeys:
[UIFont fontWithName:#"HelveticaNeue" size:14], NSFontAttributeName,
nil];
CGRect requiredHeight = [self.articles objectAtIndex:[indexPath row] boundingRectWithSize:constrainedSize
options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
attributes:attributesDictionary
context:nil];
return requiredHeight.size.height + 20;
}

Answer 4

For those who arrive here, I got the exact same issue in iOS 11 and it also happened very rarely. It turns out that I was doing some animated edits in my table view but I had 2 problems: sometimes these updates happened when the controller where this table view was placed was not on screen, so the table view had no window; other times the view controller was on screen but the animation was inside a UIView.performWithoutAnimation block (due to a bad refactor), like this:
UIView.performWithoutAnimation {
tableView.beginUpdates()
// a couple of calls to tableView.insertRows(at:with:)
// and tableView.deleteRows(at:with:)
tableView.endUpdates()
}
In my case, I removed the UIView.performWithoutAnimation and enabled the animations again, but if you need to keep the table updates without animation, I suggest that you remove the calls to tableView.beginUpdates() and tableView.endUpdates() and do the updates with animation .none, or just call tableView.reloadData().
I also did a check to see if the view controller containing this table view has the view loaded and its view.window != nil, and if not I just do a tableView.reloadData() Instead of animating the edits. Probably checking if tableView.window != nil will do the same.
I hope this helps someone :)