Iterating enum cases with CaseIterable in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of iterating enum cases with CaseIterable

What is the output of this Swift code that iterates over enum cases using CaseIterable?

Swift

enum Direction: CaseIterable {
    case north, south, east, west
}

for direction in Direction.allCases {
    print(direction)
}

A Direction.north\nDirection.south\nDirection.east\nDirection.west

B 0\n1\n2\n3

C north\nsouth\neast\nwest

D north south east west

💡 Hint

Remember that printing an enum case prints its name by default.

The CaseIterable protocol provides the allCases collection. Iterating over it and printing each case prints the case name as a string, each on its own line.

🧠 Conceptual

intermediate

Why use CaseIterable with enums?

Why is the CaseIterable protocol useful when working with enums in Swift?

A It enables enums to inherit from other enums.

B It automatically provides a collection of all enum cases for iteration.

C It allows enums to have stored properties.

D It makes enums conform to Codable automatically.

💡 Hint

Think about how you can get all enum cases without manually listing them.

CaseIterable automatically synthesizes an allCases property that lists all enum cases, making iteration easy.

🔧 Debug

advanced

Fix the error when iterating enum without CaseIterable

This code tries to iterate over enum cases but causes an error. Which option fixes the error?

Swift

enum Color {
    case red, green, blue
}

for color in Color.allCases {
    print(color)
}

A Add raw values to the enum cases.

B Change 'Color.allCases' to 'Color.cases'.

C Replace 'for' loop with 'while' loop.

D Add ': CaseIterable' to the enum declaration.

💡 Hint

The error is because 'allCases' is not available without a protocol conformance.

The allCases property is synthesized only if the enum conforms to CaseIterable.

📝 Syntax

advanced

Correct syntax for custom allCases implementation

Which option correctly implements a custom allCases property for an enum conforming to CaseIterable?

Swift

enum Fruit: CaseIterable {
    case apple, banana, cherry
    // custom allCases implementation
}

A static var allCases: [Fruit] { return [.apple, .banana, .cherry] }

B var allCases: [Fruit] { return [.apple, .banana, .cherry] }

C static func allCases() -> [Fruit] { return [.apple, .banana, .cherry] }

D let allCases = [.apple, .banana, .cherry]

💡 Hint

The allCases property must be static and return an array of enum cases.

CaseIterable requires a static property named allCases returning a collection of all cases.

🚀 Application

expert

Count enum cases using CaseIterable

Given this enum, what is the value of 'count' after the code runs?

Swift

enum Status: CaseIterable {
    case pending, approved, rejected, cancelled
}

let count = Status.allCases.count

A 4

B 3

C Compilation error

D 0

💡 Hint

Count returns the number of elements in the allCases collection.

The enum has 4 cases, so allCases.count is 4.