iOS Interview Question (Part 2)

1. Is default case is necessary in Swift’s Switch case?

No, the default case in Swift's switch statement is not necessary. It is optional and can be omitted if you don't need a fallback option for unmatched cases.

2. What is Fall-through keyword in swift?

It is used with Switch. Moves to the next case without checking its condition.

Example

let number = 2

switch number {
case 1:
    print("Case 1")
case 2:
    print("Case 2")
    fallthrough // Move to the next case
case 3:
    print("Case 3")
default:
    print("Default case")
}

// output
Case 2
Case 3

Enum:

An enum (short for enumeration) in Swift is a custom data type that groups related values together. It helps make code more readable, type-safe, and error-free.

1️⃣ Basic Enum

Enums define a set of possible values (cases).

enum Day {
    case monday, tuesday, wednesday, thursday, friday, saturday, sunday
}

var today: Day = .monday
print(today) // Output: monday

✅ No need for raw values unless required
✅ Strongly typed: You can’t assign today = "Monday" (unlike in Objective-C)

2️⃣ Enum with Raw Values

You can assign raw values to cases (e.g., Int, String).

enum StatusCode: Int {
    case success = 200
    case notFound = 404
    case serverError = 500
}

let status = StatusCode.success
print(status.rawValue) // Output: 200

✅ Use .rawValue to access the underlying value.

3️⃣ Enum with Associated Values

Each case can hold different types of associated values.

enum Payment {
    case cash(amount: Int)
    case creditCard(number: String, cvv: Int)
}

let myPayment = Payment.creditCard(number: "1234-5678-9876", cvv: 123)
switch myPayment {
case .cash(let amount):
    print("Paid \(amount) in cash")
case .creditCard(let number, let cvv):
    print("Paid using card \(number) with CVV \(cvv)")
}

✅ Each case can hold different types of data.

4️⃣ Enum with Computed Properties

Enums can have computed properties for additional logic.

enum Temperature {
    case hot, cold

    var description: String {
        switch self {
        case .hot: return "It's 🔥 hot!"
        case .cold: return "It's ❄️ cold!"
        }
    }
}
print(Temperature.hot.description) // Output: It's 🔥 hot!

✅ Adds custom behavior to enum cases.

5️⃣ Enum with Methods

Enums can include functions.

enum NetworkStatus {
    case online, offline

    func message() -> String {
        switch self {
        case .online: return "Connected ✅"
        case .offline: return "No internet ❌"
        }
    }
}
print(NetworkStatus.online.message()) // Output: Connected ✅

✅ Methods make enums more powerful and reusable.

6️⃣ Enum with Mutating Methods

Enums with mutating methods can modify self.

enum LightSwitch {
    case on, off

    mutating func toggle() {
        self = (self == .on) ? .off : .on
    }
}
var light = LightSwitch.off
light.toggle()
print(light) // Output: on

✅ mutating allows modifying the enum within a method.

7️⃣ Enum with CaseIterable

Get all enum cases using CaseIterable.

enum Beverage: CaseIterable {
    case coffee, tea, juice
}

print(Beverage.allCases.count) // Output: 3

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