No implicit fallthrough in switch in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'No implicit fallthrough in switch' mean in Swift?

In Swift, each case in a switch statement must explicitly end with a break or return. Unlike some languages, Swift does not automatically continue to the next case unless you explicitly tell it to with the 'fallthrough' keyword.

beginner

How do you make a switch case continue to the next case in Swift?

You use the 'fallthrough' keyword at the end of a case to continue execution to the next case. Without 'fallthrough', Swift stops after the current case.

intermediate

Why does Swift require explicit fallthrough instead of implicit?

Swift's design avoids bugs by preventing accidental fallthrough. This makes code clearer and safer because you must clearly state when you want to continue to the next case.

beginner

What happens if you forget to add 'break' or 'fallthrough' in a Swift switch case?

Swift automatically ends the case after its code runs. You don't need to add 'break' explicitly because Swift does not fall through by default.

beginner

Show a simple Swift switch example that uses 'fallthrough'.

Example:
let number = 2
switch number {
 case 1:
  print("One")
 case 2:
  print("Two")
  fallthrough
 case 3:
  print("Three")
 default:
  print("Other")
}
Output:
Two
Three

In Swift, what happens after a switch case finishes executing if there is no 'fallthrough'?

A It automatically continues to the next case

B It throws an error

C The switch exits and does not continue to the next case

D It repeats the current case

Swift switch cases do not fall through by default. Execution stops after the current case unless 'fallthrough' is used.

Which keyword allows a Swift switch case to continue to the next case?

A next

B continue

C break

D fallthrough

The 'fallthrough' keyword explicitly tells Swift to continue to the next case.

Why does Swift avoid implicit fallthrough in switch statements?

A To make code run faster

B To prevent accidental bugs and improve clarity

C Because it is harder to implement

D To allow multiple cases to run automatically

Explicit fallthrough prevents accidental execution of multiple cases, making code safer and clearer.

What will this Swift code print? let x = 1 switch x { case 1: print("One") case 2: print("Two") fallthrough case 3: print("Three") default: print("Other") }

A One

B One Two Three

C Two Three

D One Three

Since x is 1, only the first case runs and stops. No fallthrough is used, so it prints 'One' only.

Is the 'break' keyword required at the end of each Swift switch case?

A No, Swift does not require it

B Only if you want to stop execution

C Yes, always

D Only in default case

Swift automatically ends each case without needing 'break'.

Explain how Swift handles switch case execution and how it differs from languages with implicit fallthrough.

Think about what happens after a case runs in Swift.

Write a Swift switch statement that prints 'Low', 'Medium', or 'High' for values 1, 2, and 3, and uses 'fallthrough' to print 'Check again' after 'Medium'.

Use 'fallthrough' only where you want to continue to the next case.