Function declaration syntax in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple Swift function

What is the output of this Swift code?

Swift

func greet(name: String) -> String {
    return "Hello, \(name)!"
}

print(greet(name: "Anna"))

A greet(name: "Anna")

B Error: Missing return statement

C Hello, name!

D Hello, Anna!

💡 Hint

Look at how the function returns a string with the name inserted.

The function greet takes a string parameter and returns a greeting with that name. The print statement outputs the returned string.

❓ Predict Output

intermediate

Function with multiple parameters

What does this Swift function print?

Swift

func multiply(_ a: Int, _ b: Int) -> Int {
    return a * b
}

print(multiply(3, 4))

A 7

B 12

C 34

D Error: Missing argument labels

💡 Hint

The function multiplies two numbers and returns the result.

The function multiply takes two integers without argument labels and returns their product. 3 times 4 is 12.

❓ Predict Output

advanced

Function with default parameter values

What is the output of this Swift code?

Swift

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

greet()
greet(name: "Sam")

A Welcome, Guest!\nWelcome, Sam!

B Welcome, !\nWelcome, Sam!

C Welcome, Guest!\nWelcome, Guest!

D Error: Missing argument for parameter 'name'

💡 Hint

Default parameters are used when no argument is provided.

The first call uses the default value "Guest". The second call uses the provided argument "Sam".

❓ Predict Output

advanced

Function with inout parameter

What is the value of x after this Swift code runs?

Swift

func increment(value: inout Int) {
    value += 1
}

var x = 5
increment(value: &x)
x

A 6

B Error: Cannot pass immutable value as inout argument

C 5

D Error: Missing & before argument

💡 Hint

inout allows the function to modify the original variable.

The function increments the value by 1. Passing x with & allows the change to affect x itself.

❓ Predict Output

expert

Function with multiple return values using tuple

What does this Swift code print?

Swift

func minMax(numbers: [Int]) -> (min: Int, max: Int)? {
    guard !numbers.isEmpty else { return nil }
    var currentMin = numbers[0]
    var currentMax = numbers[0]
    for number in numbers[1...] {
        if number < currentMin {
            currentMin = number
        } else if number > currentMax {
            currentMax = number
        }
    }
    return (currentMin, currentMax)
}

if let result = minMax(numbers: [3, 7, 2, 9, 4]) {
    print("Min is \(result.min), Max is \(result.max)")
} else {
    print("Empty array")
}

A Min is 9, Max is 2

B Min is 3, Max is 7

C Min is 2, Max is 9

D Empty array

💡 Hint

The function finds the smallest and largest numbers in the array.

The function returns a tuple with the minimum and maximum values. The array contains 2 as smallest and 9 as largest.