Closures are reference types in Swift - Mini Project: Build & Apply

Closures are reference types

📖 Scenario: Imagine you have a simple counter that you want to increase by a certain number each time you call it. You will use a closure to remember the current count and add to it.

🎯 Goal: You will create a closure that keeps track of a number and adds a given value to it each time it is called. This will show how closures in Swift are reference types because they keep their own state.

📋 What You'll Learn

Create a closure that adds a number to a stored total

Create a variable to hold the closure

Call the closure multiple times to increase the total

Print the final total to show the closure kept the state

💡 Why This Matters

🌍 Real World

Closures are used in Swift for callbacks, event handlers, and to keep state in a simple way without creating classes.

💼 Career

Understanding closures as reference types helps in writing efficient Swift code for iOS apps, especially when managing state and asynchronous tasks.

1

Create a variable total and set it to 0

Create a variable called total and set it to 0 to hold the current count.

Swift

# Create a variable called total and set it to 0
# Your code here

Need a hint?

Use var total = 0 to create the variable.

2

Create a closure addToTotal that takes an Int and adds it to total

Create a closure called addToTotal that takes an Int parameter named amount and adds it to the variable total. The closure should return the new total.

Swift

var total = 0
// Create a closure called addToTotal that adds amount to total and returns total
# Your code here

Need a hint?

Use let addToTotal: (Int) -> Int = { amount in ... } and update total inside.

3

Call the closure addToTotal twice with values 5 and 3

Call the closure addToTotal with the value 5 and then call it again with the value 3. Store the results in variables firstCall and secondCall respectively.

Swift

var total = 0
let addToTotal: (Int) -> Int = { amount in
    total += amount
    return total
}
// Call addToTotal with 5 and 3, store results in firstCall and secondCall
# Your code here

Need a hint?

Call the closure like a function: addToTotal(5) and save the result.

4

Print the values of firstCall and secondCall

Print the values of firstCall and secondCall using two separate print statements to show how the closure kept the updated total.

Swift

var total = 0
let addToTotal: (Int) -> Int = { amount in
    total += amount
    return total
}

let firstCall = addToTotal(5)
let secondCall = addToTotal(3)
// Print firstCall and secondCall values
# Your code here

Need a hint?

Use print(firstCall) and print(secondCall) to show the results.