Remove top line from TabBar

removes the topline for @iOS 13.0

let appearance = tabBar.standardAppearance
appearance.shadowImage = nil
appearance.shadowColor = nil
tabBar.standardAppearance = appearance;

removes the topline for iOS 12.0 and earlier

tabBar.shadowImage = UIImage()
tabBar.backgroundImage = UIImage()

For iOS 13

if (@available(iOS 13.0, *)) {
    UITabBarAppearance *appearance = [self.tabBarController.tabBar.standardAppearance copy];
    appearance.shadowImage = nil;
    appearance.shadowColor = nil;
    self.tabBarController.tabBar.standardAppearance = appearance;
}

Tested on iOS 14

override func viewDidLoad() {
    // Remove default border line
    tabBar.shadowImage = UIImage()
    tabBar.backgroundImage = UIImage()
    tabBar.backgroundColor = UIColor.white
}

Just try to bellow code for iOS 10 :-

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    [[UITabBar appearance] setBackgroundImage:[UIImage imageNamed:@"fondoTabBar"]];
    [UITabBar appearance].layer.borderWidth = 0.0f;
    [UITabBar appearance].clipsToBounds = true;
    return YES;
}

Swift 3.x

UITabBar.appearance().layer.borderWidth = 0.0
UITabBar.appearance().clipsToBounds = true