Why Swift for Apple and beyond - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Swift code using optionals?

Consider this Swift code that uses optionals and unwrapping. What will it print?

Swift

var name: String? = "Swift"
if let unwrappedName = name {
    print("Hello, \(unwrappedName)!")
} else {
    print("No name provided.")
}

A No name provided.

B Optional("Swift")

C Hello, Swift!

D Compilation error

💡 Hint

Think about what if let does with optionals in Swift.

The if let syntax unwraps the optional name. Since name has a value, it prints "Hello, Swift!".

🧠 Conceptual

intermediate

Why does Swift use value types like structs over classes?

Swift encourages using structs (value types) instead of classes (reference types) in many cases. Why is this beneficial?

A Value types provide safer code by avoiding unintended shared state.

B Value types are slower but use less memory than classes.

C Classes cannot have methods in Swift.

D Value types allow inheritance which classes do not.

💡 Hint

Think about how copying works with value types versus reference types.

Value types are copied when assigned or passed, so changes to one copy do not affect others. This avoids bugs from shared mutable state.

🔧 Debug

advanced

What error does this Swift code produce?

Look at this Swift code snippet. What error will it cause when compiled?

Swift

let numbers = [1, 2, 3]
let first = numbers[3]
print(first)

A No error, prints nil

B Index out of range runtime error

C Prints 3

D Compilation error: Array index must be Int

💡 Hint

Remember how Swift arrays handle invalid indexes.

Accessing index 3 in an array of size 3 is out of range and causes a runtime crash.

📝 Syntax

advanced

Which option correctly declares a Swift function with a default parameter?

Choose the correct Swift function declaration that has a default value for its parameter.

A func greet(name: String = "Guest") { print("Hello, \(name)!") }

B func greet(name: String?) = "Guest" { print("Hello, \(name)!") }

C func greet(name: String = Guest) { print("Hello, \(name)!") }

D func greet(name: String default "Guest") { print("Hello, \(name)!") }

💡 Hint

Look for the correct syntax to assign a default value to a parameter.

Option A uses the correct syntax: name: String = "Guest". Others have syntax errors.

🚀 Application

expert

How many items are in the resulting dictionary after this Swift code runs?

Consider this Swift code that creates a dictionary using a dictionary literal with a condition. How many key-value pairs does the dictionary contain?

Swift

let dict = Dictionary(uniqueKeysWithValues: (1...5).map { ($0, $0 * 2) }.filter { $0.0 % 2 == 0 })
print(dict.count)

A 4

B 3

C 5

D 2

💡 Hint

Count how many numbers from 1 to 5 are even.

The filter keeps only even keys: 2 and 4. So the dictionary has 2 items.