This is the best way that I've found. You can just paste it into your appDelegate's didFinishLaunchingWithOptions
method:
Swift 3 / 4
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
// Sets background to a blank/empty image
UINavigationBar.appearance().setBackgroundImage(UIImage(), for: .default)
// Sets shadow (line below the bar) to a blank image
UINavigationBar.appearance().shadowImage = UIImage()
// Sets the translucent background color
UINavigationBar.appearance().backgroundColor = .clear
// Set translucent. (Default value is already true, so this can be removed if desired.)
UINavigationBar.appearance().isTranslucent = true
return true
}
Swift 2.0
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// Override point for customization after application launch.
// Sets background to a blank/empty image
UINavigationBar.appearance().setBackgroundImage(UIImage(), forBarMetrics: .Default)
// Sets shadow (line below the bar) to a blank image
UINavigationBar.appearance().shadowImage = UIImage()
// Sets the translucent background color
UINavigationBar.appearance().backgroundColor = UIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.0)
// Set translucent. (Default value is already true, so this can be removed if desired.)
UINavigationBar.appearance().translucent = true
return true
}
source: Make navigation bar transparent regarding below image in iOS 8.1