Switch must be exhaustive in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean for a switch statement to be exhaustive in Swift?

It means the switch must cover all possible cases of the value being checked, so no case is left unhandled.

beginner

Why does Swift require switch statements to be exhaustive?

To ensure safety by forcing the programmer to handle every possible value, preventing unexpected behavior at runtime.

beginner

How can you make a switch statement exhaustive when you don't want to handle all cases explicitly?

You can add a default case to catch all remaining values.

intermediate

Given an enum with 3 cases, what happens if you write a switch statement that only handles 2 cases without a default?

The code will not compile because the switch is not exhaustive; the missing case must be handled or a default added.

intermediate

Can switch statements on non-enum types be exhaustive in Swift?

Yes, but only by using a default case because non-enum types can have many values.

What keyword can you use to make a switch statement exhaustive without listing all cases?

A default

B else

C catch

D final

The default case catches all values not explicitly handled, making the switch exhaustive.

If you have an enum with 4 cases, how many cases must your switch statement handle to be exhaustive?

A All 4 or use default

B None, switch is always exhaustive

C Only 1

D At least 3

You must handle all 4 cases explicitly or add a default case to cover any unhandled cases.

What happens if a switch statement on an enum is not exhaustive in Swift?

A It compiles but crashes at runtime

B It compiles with a warning

C It does not compile

D It runs but skips missing cases

Swift requires exhaustive switches on enums, so missing cases cause a compile-time error.

Can you omit the default case if your switch covers all enum cases?

A No, default is always required

B Yes, if all cases are covered

C Only if enum has less than 3 cases

D Only for integer types

If all enum cases are explicitly handled, the switch is exhaustive without a default.

Why might you prefer to list all enum cases explicitly instead of using default?

A To avoid runtime errors

B To make code shorter

C To improve performance

D To get compiler errors if new cases are added later

Explicit cases help catch missing cases when enums change, improving code safety.

Explain what it means for a switch statement to be exhaustive in Swift and why it is important.

Think about how Swift prevents missing cases in switch.

Describe how you can make a switch statement exhaustive when working with enums and when working with other types.

Consider differences between enums and other types.