[Solved] What is the error in the following code that causes a crash when performing the segue?override func prepare(for segue: UIStoryboardSegue, sender: Any?) { let destinationVC = segue.destination as!... | iOS Swift

iOS Swift - Navigation

What is the error in the following code that causes a crash when performing the segue?

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  let destinationVC = segue.destination as! DetailViewController
  destinationVC.data = "Hello"
}

AAssigning data after the segue completes

BUsing forced cast instead of optional cast

CMissing check for segue.identifier before casting

DNot calling super.prepare(for:sender:)

Step-by-Step Solution

Solution:

Step 1: Identify missing segue identifier check
The code casts destinationVC without checking if the segue.identifier matches the expected one, risking wrong destination type.
Step 2: Understand crash cause
If the segue is not to DetailViewController, forced cast fails and crashes the app.
Final Answer:
Missing check for segue.identifier before casting -> Option C
Quick Check:
Always check segue.identifier before casting [OK]

Quick Trick: Always check segue.identifier before casting destination [OK]

Common Mistakes:

Skipping identifier check causes crash
Assuming forced cast is always safe
Ignoring optional cast or guard statements

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More iOS Swift Quizzes

What is the error in the following code that causes a crash when performing the segue?

Step 1: Identify missing segue identifier check

Step 2: Understand crash cause

Final Answer:

Quick Check:

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