Closure expression syntax in Swift - Mini Project: Build & Apply

Closure Expression Syntax in Swift

📖 Scenario: Imagine you are organizing a small event and you have a list of guest names. You want to sort this list alphabetically but with a twist: you want to sort it in reverse order using a simple function. Swift closures let you write this sorting logic in a neat and short way.

🎯 Goal: You will create a list of guest names, then write a closure expression to sort the list in reverse alphabetical order, and finally print the sorted list.

📋 What You'll Learn

Create an array called guests with the exact names: "Anna", "Brian", "Craig", "Diana"

Create a closure expression called reverseSort that takes two String parameters and returns Bool indicating if the first string should come before the second in reverse alphabetical order

Use the reverseSort closure to sort the guests array

Print the sorted guests array

💡 Why This Matters

🌍 Real World

Closures are used in Swift to write short, reusable blocks of code that can be passed around, like sorting lists or handling user actions.

💼 Career

Understanding closure syntax is important for iOS app development and working with Swift frameworks that use closures for callbacks and event handling.

1

Create the guest list

Create an array called guests with these exact names: "Anna", "Brian", "Craig", "Diana"

Swift

# Create the guests array with the exact names
# Your code here

Need a hint?

Use square brackets [] to create an array and separate names with commas.

2

Create the reverse sort closure

Create a closure expression called reverseSort that takes two String parameters named a and b and returns Bool. The closure should return true if a is greater than b (to sort in reverse alphabetical order).

Swift

var guests = ["Anna", "Brian", "Craig", "Diana"]

// Create the reverseSort closure here
# Your code here

Need a hint?

Use the closure syntax: { (parameters) -> returnType in statements }.

3

Sort the guests using the closure

Use the reverseSort closure to sort the guests array and assign the result back to guests.

Swift

var guests = ["Anna", "Brian", "Craig", "Diana"]

let reverseSort = { (a: String, b: String) -> Bool in
    return a > b
}

// Sort guests using reverseSort closure
# Your code here

Need a hint?

Use the sorted(by:) method with the closure as argument.

4

Print the sorted guest list

Print the guests array to show the sorted names.

Swift

var guests = ["Anna", "Brian", "Craig", "Diana"]

let reverseSort = { (a: String, b: String) -> Bool in
    return a > b
}

guests = guests.sorted(by: reverseSort)

// Print the sorted guests array
# Your code here

Need a hint?

Use print(guests) to display the array.