How do I diagnose and fix 'fatal error: Index out of range' in Swift/Xcode?

In Swift, the 'fatal error: Index out of range' is a common runtime error that occurs when you attempt to access an array index that does not exist. This typically happens when you try to access elements using an index that is either negative or greater than or equal to the array's count. Diagnosing this error involves checking the array's bounds before accessing elements.

How to Diagnose the Error

  • Check the array's count using the `.count` property.
  • Print the index you are trying to access to ensure it's within the valid range.
  • Use conditional statements to prevent access to invalid indices.

How to Fix the Error

To fix 'Index out of range' errors, make sure your index is valid. You can do this by using optional binding or guard statements:

let array = [1, 2, 3] let index = 3 // Check if the index is within bounds if index < array.count { print(array[index]) } else { print("Index out of range") }

By ensuring that you only access valid indices, you can prevent this error from occurring in your Swift applications.


Swift Index out of range fatal error runtime error array access Swift debugging

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