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Why does this code cause a crash? let newVC: UIViewController? = nil navigationController?.pushViewController(newVC!, animated: true)

medium📝 Debug Q7 of 15
iOS Swift - Navigation
Why does this code cause a crash? let newVC: UIViewController? = nil navigationController?.pushViewController(newVC!, animated: true)
Aanimated parameter cannot be true
BYou cannot push a nil view controller onto the navigation stack
CnavigationController must be force unwrapped
DpushViewController requires a completion handler
Step-by-Step Solution
Solution:

  1. Step 1: Understand pushViewController parameter

    pushViewController requires a non-nil UIViewController instance.

  2. Step 2: Check consequences of nil argument

    Passing nil (via force-unwrap newVC!) causes runtime crash because method expects a valid controller.

  3. Final Answer:

    You cannot push a nil view controller onto the navigation stack -> Option B

  4. Quick Check:

    pushViewController(nil) causes crash [OK]
Quick Trick: Never push nil view controller; always instantiate first [OK]
Common Mistakes:
  • Passing nil instead of a valid view controller
  • Thinking animated parameter causes crash
  • Believing force unwrap is required

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