How to Navigate from one View Controller to another using Swift

Create a swift file (SecondViewController.swift) for the second view controller and in the appropriate function type this:

let secondViewController = self.storyboard.instantiateViewControllerWithIdentifier("SecondViewController") as SecondViewController
self.navigationController.pushViewController(secondViewController, animated: true)

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Swift 2+

let mapViewControllerObj = self.storyboard?.instantiateViewControllerWithIdentifier("MapViewControllerIdentifier") as? MapViewController
self.navigationController?.pushViewController(mapViewControllerObj!, animated: true)

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Swift 4

let vc = UIStoryboard.init(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "IKDetailVC") as? IKDetailVC
self.navigationController?.pushViewController(vc!, animated: true)

In my experience navigationController was nil so I changed my code to this:

let next = self.storyboard?.instantiateViewControllerWithIdentifier("DashboardController") as! DashboardController
self.presentViewController(next, animated: true, completion: nil)

Don't forget to set ViewController StoryBoard Id in StoryBoard -> identity inspector

If you don't want the back button to appear (which was my case, because I wanted to present after a user logged in) here is how to set the root of the nav controller:

let vc = self.storyboard?.instantiateViewControllerWithIdentifier("YourViewController") as! YourViewController
        let navigationController = UINavigationController(rootViewController: vc)
        self.presentViewController(navigationController, animated: true, completion: nil)