No implicit fallthrough in switch in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of switch without explicit fallthrough

What will be the output of this Swift code snippet?

Swift

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

A Other

B Two\nThree

C One\nTwo

D Two

💡 Hint

Remember that Swift switch cases do not fall through by default.

In Swift, each case in a switch statement is exclusive and does not continue to the next case unless you explicitly use the 'fallthrough' keyword. So only 'Two' is printed.

❓ Predict Output

intermediate

Effect of fallthrough keyword in Swift switch

What will be printed when this Swift code runs?

Swift

let value = 1
switch value {
case 1:
    print("Start")
    fallthrough
case 2:
    print("Middle")
case 3:
    print("End")
default:
    print("Default")
}

A Start\nMiddle

B Start

C Start\nMiddle\nEnd

D Middle

💡 Hint

Check what the 'fallthrough' keyword does in Swift switch cases.

The 'fallthrough' keyword causes execution to continue to the next case without checking its condition. So 'Start' and then 'Middle' are printed.

🔧 Debug

advanced

Why does this Swift switch code not compile?

Identify the reason this Swift code causes a compile error.

Swift

let x = 5
switch x {
case 1:
    print("One")
case 2:
    print("Two")
case 3:
    print("Three")
}

A Variable x must be mutable (var) to use in switch

B Switch cases must have fallthrough keyword

C Missing default case causes compile error

D Print statements must be inside braces

💡 Hint

Swift switch statements must be exhaustive for non-enum types.

Since x is an Int, the switch must cover all possible values or include a default case. Missing default causes a compile error.

🧠 Conceptual

advanced

Understanding no implicit fallthrough in Swift switch

Which statement best describes Swift's switch behavior regarding fallthrough?

A Swift switch cases never fall through unless 'fallthrough' keyword is explicitly used

B Swift switch requires 'continue' keyword to fall through cases

C Swift switch cases automatically fall through to the next case unless 'break' is used

D Swift switch cases fall through only if cases share the same code block

💡 Hint

Think about how Swift differs from C-like languages in switch behavior.

Swift requires explicit 'fallthrough' to continue to the next case. Without it, execution stops after the matched case.

🚀 Application

expert

Predict the output with multiple fallthroughs in Swift switch

What is the output of this Swift code?

Swift

let n = 1
switch n {
case 1:
    print("A")
    fallthrough
case 2:
    print("B")
    fallthrough
case 3:
    print("C")
default:
    print("D")
}

A A\nB

B A\nB\nC

C A

D A\nB\nC\nD

💡 Hint

Each fallthrough moves execution to the next case regardless of its condition.

Starting at case 1, prints 'A', then fallthrough to case 2 prints 'B', then fallthrough to case 3 prints 'C'. Default is not reached.