Data problem of iPhone UITableController

I am new to iPhone development, and I recently encounter a very strange problem with UITableController. I implemented a very simple program with UITableController where it has a datasource of an array of TestClass, where TestClass is a simple class I defined containing only a NSString attribute. The problem is that I can display the table, but when I select a cell and goes to didSelectRowAtIndexPath method, my datasource cannot be found anymore. And my program works well if I switch the datasource to an array of NSString instead of self-defined class. What's the problem of it?

- (id)initWithStyle:(UITableViewStyle)style {
    if (self = [super initWithStyle:style]) {
        self.title = @"TV Shows";
        self.navigationItem.backBarButtonItem.title = @"Shows";
        self.t = [NSArray arrayWithObjects:[[TestClass alloc] initWithTest:@"test"], nil];
    }
    return self;
}


- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    **NSLog(t); //NSException here**
    TVAppDelegate *delegate = [[UIApplication sharedApplication] delegate];
    delegate.selectedShow = indexPath;
    ShowCharactersTableViewController *showCharactersController = [[ShowCharactersTableViewController alloc开发者_Go百科] initWithStyle:UITableViewStylePlain];
    [[delegate navigationController] pushViewController:showCharactersController animated:YES];
    [showCharactersController release];
}

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Try:

NSLog(@"%@",t);

It will print the description of the t object. t is not a litteral string, so it can't be logged directly, you have to use a format. (Didn't you get a warning?)