How to remove border of the navigationBar in swift?

i've been trying to remove the navigationBars border without luck. I've researched and people seem to tell to set shadowImage and BackgroundImage to nil, but this does not work in my case.

My code

    self.navigationController?.navigationBar.barTintColor = UIColor(rgba: "#4a5866")
    self.navigationController?.navigationBar.setBackgroundImage(UIImage(named: ""), forBarMetrics: UIBarMetrics.Default)
    self.navigationController?.navigationBar.shadowImage = UIImage(named: "")

illustration:

The trouble is with these two lines:

self.navigationController?.navigationBar.setBackgroundImage(UIImage(named: ""), forBarMetrics: UIBarMetrics.Default)
self.navigationController?.navigationBar.shadowImage = UIImage(named: "")

Since you don't have an image with no name, UIImage(named: "") returns nil, which means the default behavior kicks in:

When non-nil, a custom shadow image to show instead of the default shadow image. For a custom shadow to be shown, a custom background image must also be set with -setBackgroundImage:forBarMetrics: (if the default background image is used, the default shadow image will be used).

You need a truly empty image, so just initialize with UIImage():

self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: UIBarMetrics.default)
self.navigationController?.navigationBar.shadowImage = UIImage()

Swift 4 & Swift 5

Removing border:

self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for:.default)
self.navigationController?.navigationBar.shadowImage = UIImage()
self.navigationController?.navigationBar.layoutIfNeeded()

Restoring border:

self.navigationController?.navigationBar.setBackgroundImage(nil, for:.default)
self.navigationController?.navigationBar.shadowImage = nil
self.navigationController?.navigationBar.layoutIfNeeded()

With Swift 2 you can do it this way:

AppDelegate file

Inside func application(..., didFinishLaunchingWithOptions launchOptions:...)

UINavigationBar.appearance().shadowImage = UIImage()
UINavigationBar.appearance().setBackgroundImage(UIImage(), forBarMetrics: .Default)

for Swift 3:

UINavigationBar.appearance().shadowImage = UIImage()
UINavigationBar.appearance().setBackgroundImage(UIImage(), for: .default)