Functions as types in Swift - Mini Project: Build & Apply

Functions as Types in Swift

📖 Scenario: You are building a simple calculator app that can perform different math operations. Each operation is a function that takes two numbers and returns a number.

🎯 Goal: Learn how to use functions as types by creating variables that hold functions, then calling them to perform calculations.

📋 What You'll Learn

Create a function variable with a specific function type

Assign different functions to the function variable

Call the function variable with arguments

Print the result of the function call

💡 Why This Matters

🌍 Real World

Using functions as types lets you write flexible code that can change behavior by swapping functions. This is useful in apps like calculators, games, or any place where you want to choose actions dynamically.

💼 Career

Understanding functions as types is important for Swift developers to write clean, reusable, and flexible code. It is a foundation for advanced topics like closures, callbacks, and functional programming.

1

Create two functions for addition and subtraction

Write two functions called add and subtract. Both take two Int parameters and return an Int. add returns the sum, subtract returns the difference.

Swift

# Write the add and subtract functions below
// Your code here

Need a hint?

Define two functions with the same parameter and return types but different bodies.

2

Create a function variable with type (Int, Int) -> Int

Create a variable called operation of type (Int, Int) -> Int. Assign the add function to operation.

Swift

func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}

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

// Create a variable called operation of type (Int, Int) -> Int and assign add to it
// Your code here

Need a hint?

Use the exact variable name operation and assign add without parentheses.

3

Change the function variable to subtract and call it

Assign the subtract function to the operation variable. Then call operation with arguments 10 and 4, and store the result in a variable called result.

Swift

func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}

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

var operation: (Int, Int) -> Int = add

// Assign subtract to operation
// Call operation with 10 and 4 and store in result
// Your code here

Need a hint?

Assign subtract to operation and call it with 10 and 4.

4

Print the result of the operation

Print the value of the result variable using print.

Swift

func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}

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

var operation: (Int, Int) -> Int = add

operation = subtract
let result = operation(10, 4)

// Print the result variable
// Your code here

Need a hint?

Use print(result) to show the output.