main.m

#import <UIKit/UIKit.h>

int main(int argc, char *argv[]) {
    
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    int retVal = UIApplicationMain(argc, argv, nil, @"RoundedCornerTestAppDelegate");
    [pool release];
    return retVal;
}

RoundedCornerTestAppDelegate.h

#import <UIKit/UIKit.h>

@interface RoundedCornerTestAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window_;
}

@end

RoundedCornerTestAppDelegate.m

#import "RoundedCornerTestAppDelegate.h"
#import <QuartzCore/QuartzCore.h>

@implementation RoundedCornerTestAppDelegate

- (void)applicationDidFinishLaunching:(UIApplication *)application {
  window_ = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  
  UINavigationBar *navBar = [[UINavigationBar alloc] initWithFrame:CGRectMake(0, 20, 320, 42)];
  
  [window_ addSubview:navBar];
  
  UIView *tab = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, 75, 40)] autorelease];
  tab.backgroundColor = [UIColor colorWithRed:228.0/255.0
                                        green:230.0/255.0
                                         blue:235.0/255.0
                                        alpha:1];
  tab.layer.cornerRadius = 5;
  
  UIView *tabContainer = [[[UIView alloc] initWithFrame:CGRectMake(0, 5, 75, 35)] autorelease];
  tabContainer.clipsToBounds = YES;
  [tabContainer addSubview:tab];
  
  [navBar addSubview:tabContainer];
  
  [window_ makeKeyAndVisible];
}


- (void)dealloc {
  [window_ release];
  [super dealloc];
}

@end