Iphone - when to calculate heightForRowAtIndexPath for a tableview when each cell height is dynamic?

Question

I have seen this question asked many times but astoundingly, I have not seen a consistent answer, so I will give it a try myself:

If you have a tableview containing

Answer 1

as i searched over and over about this topic, finally this logic came to my thought. a simple code, but maybe not efficient enough, but so far it's the best i can find.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
  NSDictionary * Object=[[NSDictionary alloc]init];
  Object=[Rentals objectAtIndex:indexPath.row];
  static NSString *CellIdentifier = @"RentalCell";
  RentalCell *cell = (RentalCell *)[tableView
                                  dequeueReusableCellWithIdentifier:CellIdentifier];
  if (cell == nil)
  {
      cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
  }
   NSString* temp=[Object objectForKey:@"desc"];
   int lines= (temp.length/51)+1;
   //so maybe here, i count how many characters that fit in one line in this case 51
   CGRect correctSize=CGRectMake(cell.infoLabel.frame.origin.x, cell.infoLabel.frame.origin.y,    cell.infoLabel.frame.size.width, (15*lines));
   //15 (for new line height)
   [cell.infoLabel setFrame:correctSize];
   //manage your cell here
}

and here is the rest of the code

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

    NSDictionary * Object=[[NSDictionary alloc]init];
    Object=[Rentals objectAtIndex:indexPath.row];
    static NSString *CellIdentifier = @"RentalCell";
    RentalCell *cells = (RentalCell *)[tableView
                                  dequeueReusableCellWithIdentifier:CellIdentifier];
    NSString* temp=[Object objectForKey:@"desc"];
    int lines= temp.length/51;

    return (CGFloat) cells.bounds.size.height + (13*lines);
}