Enum with switch pattern matching in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an enum in Swift?

An enum (short for enumeration) is a type that groups related values under a common name. It helps organize code by defining a set of possible cases.

beginner

How does switch pattern matching work with enums in Swift?

Switch pattern matching lets you check which enum case a value matches and run code for that case. It can also extract associated values if the enum has them.

intermediate

What happens if you don’t cover all enum cases in a switch statement?

Swift requires all enum cases to be handled in a switch. If not, you must add a default case or the code won’t compile.

intermediate

How do you extract associated values from an enum case in a switch?

Use case pattern matching with let or var to bind the associated values to variables inside the switch case.

beginner

Example: What does this code print?
<pre>enum Direction { case north, south, east, west }
let dir = Direction.east
switch dir {
 case .north: print("Up")
 case .south: print("Down")
 case .east: print("Right")
 case .west: print("Left")
}</pre>

It prints "Right" because the value dir is .east and the switch matches that case.

What keyword is used to define an enum in Swift?

A class

B struct

C enum

D type

The keyword 'enum' is used to define an enumeration in Swift.

What must a switch statement do when matching an enum?

A Handle all enum cases or include a default case

B Only handle one case

C Ignore cases without code

D Use if-else instead

Swift requires switch statements to be exhaustive, meaning all enum cases must be handled or a default case must be provided.

How do you access associated values in a switch case?

A Use a function call

B Use let or var to bind values in the case pattern

C Use dot notation outside the switch

D You cannot access associated values

You use let or var inside the case pattern to extract associated values from an enum case.

Which of these is a valid enum case pattern in a switch?

A case .north:

B case north:

C case Direction.north:

D case "north":

Inside a switch on an enum, you use the shorthand '.caseName' to match cases.

What will happen if you forget to handle an enum case in a switch without a default?

A Code runs but skips missing cases

B Runtime error

C Switch ignores missing cases

D Compilation error

Swift enforces exhaustiveness in switch statements on enums, so missing cases cause a compile-time error.

Explain how to use switch pattern matching with enums in Swift, including handling associated values.

Think about how you check each case and get values out if needed.

Describe why Swift requires switch statements on enums to be exhaustive and how you can satisfy this requirement.

Consider safety and completeness in your code.