Use didSelectRowAtIndexPath or prepareForSegue method for UITableView?

If you use prepareForSegue:sender:then you won't have as much to change if you later decide to trigger the segue from some control outside the table view.

The prepareForSegue:sender: message is sent to the current view controller, so I'd suggest something like this:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Assume self.view is the table view
    NSIndexPath *path = [self.tableView indexPathForSelectedRow];
    DetailObject *detail = [self detailForIndexPath:path];
    [segue.destinationViewController setDetail:detail];
}

In Swift:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    let path = self.tableView.indexPathForSelectedRow()!
    segue.destinationViewController.detail = self.detailForIndexPath(path)
}

I did this and it worked

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{

    NSLog(@"Row Selected = %i",indexPath.row);

    [self performSegueWithIdentifier:@"testID" sender:self.view];    
}

When sender is UITableViewCell, you may ask UITableView to query indexPath of the cell.

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if let cell = sender as? UITableViewCell {
            let indexPath = self.tableView.indexPathForCell(cell)!
            assert(segue.destinationViewController.isKindOfClass(DetailViewController))
            let detailViewController = segue.destinationViewController as! DetailViewController
            detailViewController.item = self.items[indexPath.row] // like this
        }
    }

if your tableView property is in another class and you only have one section, then you could use the tag property to store the cell's row like:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];

     cell.tag = indexPath.row;

     return cell;
}

And then you can access it as the sender is the same cell with the row value in its tag:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    MyDestinationViewController *destinationViewController = segue.destinationViewController;
    destinationViewController.myProperty = [tableViewElementsArray objectAtIndex:[sender tag]]; // sender will be your cell 
}