tableView:indexPathForCell returns nil

I am using the method tableView:indexPathForCell开发者_JAVA技巧 to implement a custom delegate that can dynamically resize a UITableViewCell based on the frame size of the UIWebView that is inside of it. The problem is that tableView:indexPathForCell is returning nil when I try to find out what the indexPath of a particular cell is:

- (void)trialSummaryTableViewCell:(TrialSummaryTableViewCell *)cell shouldAssignHeight:(CGFloat)newHeight {
    NSIndexPath *indexPath = [tableV indexPathForCell:cell];
    NSLog(@"tableV: %@\ncell: %@\nindexPath: %@", tableV, cell, indexPath); //<-- 
    // ...
}

Here, tableV does not return nil, cell does not return nil, but indexPath returns nil.

What am I doing wrong?

Edit: I am calling -(void)trialSummaryTableViewCell from the tableView:cellForRowAtIndexPath: method

It could be that the cell is not visible at this moment. tableView:indexPathForCell returns nil in this situation. I solved this using indexPathForRowAtPoint this method works even if the cell is not visible. The code:

UITableViewCell *cell = textField.superview.superview;
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:cell.center];

[tableV indexPathForCell:cell] returns nil if cell is not visible.

Also if you are calling "trialSummaryTableViewCell" from the "cellForRowAtIndexPath" method, you could easily pass indexPath also to the "trialSummaryTableViewCell" method.

A small update, since Jorge Perez' answer will fail starting at iOS7 (since a UIScrollView has been inserted and calling textField.superview.superview won't work anymore).

You can retrieve the NSIndexPath like this:

//find the UITableViewCell superview
UIView *cell = textField;
while (cell && ![cell isKindOfClass:[UITableViewCell class]])
    cell = cell.superview;

//use the UITableViewCell superview to get the NSIndexPath
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:cell.center];