Why can't I use variableHeightRows in three20?

In my TTTableViewController subclass, I'm setting variableHeightRows = YES. In my TTTableViewCell subclass, I've implemented

+ (CGFloat)tableView:(UITableView*)tableView rowHeightForObject:(id)object

The cell height is not varying at all, and Three20 doesn't even appear to be calling the rowHeightForObject method - I set a breakpoint inside it and during 开发者_如何学Cdebugging it never hit my breakpoint. What am I doing wrong? Is there something else I need to set?

I've never encountered any problems with variableHeightRows, so just to throw out some random things to try:

• Are you sure the line executing variableHeightRows = YES is being called? Have you set a breakpoint there?
• Are you sure your subclass is actually the one populating the table (you've set it up properly in your data source). Maybe try setting a breakpoint somewhere else in the subclass.