returning null inside tableview delegate - iphone

Question

HI
I am working on UITablview based project. i like to load a new view when ever a cell got click. i am using following code in didselectRowAtIndexPath delegate method.
The below coding is not showing any error but new view not get load and [self navigationController] is returning null.
inside Viewdidload function [self navigationcontroller] returning proper value. but inside Delegate method [self navigationcontroller] returns null.
/// inside appDelegate class
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
self.viewController = [[LAMainViewController_iPhone alloc]initWithNibName:#"LAMainViewController_iPhone" bundle:nil];
UINavigationController *controller = [[UINavigationController alloc]initWithRootViewController:viewController];
[window addSubview:controller.view];
[controller release];
[window makeKeyAndVisible];
return YES;
}
/// inside LAmainviewcontroller.m
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
// Custom initialization
}
//self.navigationController.navigationBar.backgroundColor =[UIColor clearColor];// .title=#"test";
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
NSString *materialPlistPath = [[NSBundle mainBundle]pathForResource:#"materials" ofType:#"plist"];
materialList = [[NSArray alloc]initWithContentsOfFile:materialPlistPath];
materialTable.backgroundColor = [UIColor blackColor];
NSLog(#" dud kiad navigationController %#", self.navigationController);
//2010-10-20 15:22:03.809 LabAssistant[17368:207] dud kiad navigationController <UINavigationController: 0x5f3b160>
}
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:YES];
self.navigationController.navigationBarHidden = YES;
NSIndexPath *indexPath = [materialTable indexPathForSelectedRow];
[materialTable deselectRowAtIndexPath:indexPath animated:YES];
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
LAMaterialPropertiesViewController_iPhone *materialPropertyListView = [[[LAMaterialPropertiesViewController_iPhone alloc] initWithNibName:#"LAMaterialPropertiesViewController_iPhone" bundle:nil] autorelease];
materialPropertyListView.chemicalName = [[materialList objectAtIndex:[indexPath row]] objectForKey:#"materialProperty"];
[[self navigationController] pushViewController:materialPropertyListView animated:YES];
NSLog(#"%#",[self navigationController]);
///2010-10-20 16:20:42.634 LabAssistant[17656:207] navigationController (null)
}
please help me to fix this issue.
thanks!

Answer 1

Remove the autorelease from the init statement. Actually the viewcontroller is getting released before it gets pushed.
instead of
LAMaterialPropertiesViewController_iPhone *materialPropertyListView = [[[LAMaterialPropertiesViewController_iPhone alloc] initWithNibName:#"LAMaterialPropertiesViewController_iPhone" bundle:nil] autorelease];
try this
LAMaterialPropertiesViewController_iPhone *materialPropertyListView = [[LAMaterialPropertiesViewController_iPhone alloc] initWithNibName:#"LAMaterialPropertiesViewController_iPhone" bundle:nil];
Hope this will solve your problem.

Answer 2

I think the table view delegate is called before the navigation controller is set to the view controller.
Can you try reloading the tableview [tableview reloadData]; in viewWillAppear or viewDidAppear?