How to calculate number lines required for text - objective-c

Question

I know this is going to be a stupid daft simple question but I'm going round in circles.
I have several strings which i want displaying in a uitableview. Some of these strings are very long. I have previously asked how to calculate the cell height, and choose the following answer:
- (CGFloat)cellHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellString = <YOUR MODEL OBJECT>;
NSDictionary *attributes = #{ NSFontAttributeName : [UIFont systemFontOfSize:16.0f] };
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc]
initWithString: cellString
attributes:attributes];
CGFloat width = self.tableView.frame.size.width - 32.0f;
CGRect frame = [attributedString boundingRectWithSize:CGSizeMake(width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin context:nil];
// Add some extra padding to the height
CGFloat height = frame.size.height + 16.0f;
return ceil(height);
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return [self cellHeightForRowAtIndexPath:indexPath];
}
how can I get the number of lines required in the uitableview to display the strings.

Answer 1

The best way to actually calculate a cell height is to use a prototype cell for calculating the height.
Add a property to your interface extension:
#interface TableViewController ()
#property (nonatomic, strong) TableViewCell *prototypeCell;
#end
Then lazily load it:
- (TableViewCell *)prototypeCell
{
if (!_prototypeCell)
{
_prototypeCell = [[TableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"Prototype"];
}
return _prototypeCell;
}
Change your -[tableView:cellForRowAtIndexPath:] method to use a -[configureCell:forRowAtIndexPath:] type pattern:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
TableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"CellId" forIndexPath:indexPath];
[self configureCell:cell forRowAtIndexPath:indexPath];
return cell;
}
-(void)configureCell:(TableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
// Set up you cell from your model
}
Now use this method to setup your prototype and then use the height of that for -[tableView:heightForRowAtIndexPath:]:
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
[self configureCell:self.prototypeCell forRowAtIndexPath:indexPath];
[self.prototypeCell layoutIfNeeded];
CGSize size = [self.prototypeCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
return ceil(size.height);
}