Why do Navigation Controllers Access Views from The Storyboard? - ios

Question

In various tutorials on how to use SegmentControllers, TabBarControllers, etc. it is configured such that the variable representing the view gets its value from an instantiation of the storyboard:
private lazy var summaryViewController: SummaryViewController = {
// Load Storyboard
let storyboard = UIStoryboard(name: "Main", bundle: Bundle.main)
// Instantiate View Controller
var viewController = storyboard.instantiateViewController(withIdentifier: "SummaryViewController") as! SummaryViewController
// Add View Controller as Child View Controller
self.add(asChildViewController: viewController)
return viewController
}()
Why does this code not just get an instance of SummaryViewController?

Answer 1

Adding an instance of a VC from your Storyboard, adds all of the logic and outlets you add in the storyboard. Let's say you have the following (obviously simple) VC:
class MyVC : UIViewController {
func viewDidLoad() {
}
#IBAction buttonPressed(sender : UIButton) {
/// Do something
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "mySegue"{
var vc = segue.destinationViewController as! WhateverViewController
}
}
}
where the buttonPressed: func is connected to a button in IB, and you also have a segue with a 'mySegue' identifier. Initializing your VC from the storyboard gives you access to all of these things. You absolutely can instantiate and push a VC, without the use of the storyboard, but you should not do so, when the VC you are pushing has wired IBOutlets, IBActions, etc.... If you want to do this in code, try the following:
let myNewVC = PushedViewController()
self.navigationController?.pushViewController(myNewVC, animated : true)
This will push the myNewVC onto your navigation stack, back button and all, and without using the storyboard.