Why ARC matters for Swift developers - See It in Action

Why ARC matters for Swift developers

📖 Scenario: Imagine you are building a simple app that manages a list of books. Each book has a title and an author. You want to understand how Swift manages memory automatically to keep your app running smoothly without crashes or slowdowns.

🎯 Goal: You will create a small Swift program that shows how Automatic Reference Counting (ARC) works by creating and releasing objects. This will help you see why ARC is important for managing memory in Swift apps.

📋 What You'll Learn

Create a class called Book with properties title and author

Create a variable called book1 and assign it a Book instance

Create a second variable called book2 and assign it the same instance as book1

Set book1 to nil and observe that the object is still kept alive by book2

Set book2 to nil and observe that the object is deallocated

💡 Why This Matters

🌍 Real World

Memory management is crucial in apps to keep them fast and stable. ARC helps Swift developers avoid manual memory handling.

💼 Career

Understanding ARC is essential for Swift developers to write efficient, bug-free code and maintain app performance.

1

Create the Book class

Create a class called Book with two properties: title and author, both of type String. Add an initializer to set these properties. Also add a deinit method that prints "Book titled \"\(title)\" is being deallocated".

Swift

# Define the Book class with title and author properties
# Your code here

Need a hint?

Remember to use deinit to see when the object is removed from memory.

2

Create the first reference to a Book instance

Create a variable called book1 and assign it a new Book instance with the title "Swift Programming" and author "Apple".

Swift

class Book {
    let title: String
    let author: String
    
    init(title: String, author: String) {
        self.title = title
        self.author = author
    }
    
    deinit {
        print("Book titled \"\(title)\" is being deallocated")
    }
}

// Create book1 instance
# Your code here

Need a hint?

Use var book1: Book? = Book(title: "Swift Programming", author: "Apple") to create the instance.

3

Create a second reference to the same Book instance

Create a variable called book2 and assign it the same instance as book1.

Swift

class Book {
    let title: String
    let author: String
    
    init(title: String, author: String) {
        self.title = title
        self.author = author
    }
    
    deinit {
        print("Book titled \"\(title)\" is being deallocated")
    }
}

var book1: Book? = Book(title: "Swift Programming", author: "Apple")

// Assign book2 to the same instance as book1
# Your code here

Need a hint?

Just assign book2 = book1 to share the same object.

4

Set references to nil and observe deallocation

Set book1 to nil. Then set book2 to nil. This will show when the Book instance is deallocated by ARC.

Swift

class Book {
    let title: String
    let author: String
    
    init(title: String, author: String) {
        self.title = title
        self.author = author
    }
    
    deinit {
        print("Book titled \"\(title)\" is being deallocated")
    }
}

var book1: Book? = Book(title: "Swift Programming", author: "Apple")
var book2: Book? = book1

// Set book1 and book2 to nil to trigger deallocation
# Your code here

Need a hint?

Setting both references to nil lets ARC remove the object and call deinit.