Actor declaration syntax in Swift - Mini Project: Build & Apply

Actor declaration syntax

📖 Scenario: Imagine you are building a simple app that manages a shared counter safely across multiple parts of your program. You want to use Swift's actor to protect the counter from being changed at the same time by different parts.

🎯 Goal: You will create an actor named Counter that holds a number and safely increases it. Then you will print the current value.

📋 What You'll Learn

Create an actor named Counter with a variable value initialized to 0

Add a function increment() inside the actor that increases value by 1

Create an instance of Counter named myCounter

Call increment() on myCounter and print the updated value

💡 Why This Matters

🌍 Real World

Actors are used in Swift apps to safely manage data that many parts of the app might want to change at the same time, like counters, user settings, or shared resources.

💼 Career

Understanding actors is important for Swift developers working on apps that use concurrency, such as iOS or macOS apps that need to be fast and safe.

1

Create an actor with a value variable

Write an actor named Counter that has a variable value set to 0 inside it.

Swift

# Write the actor declaration with a variable named value set to 0
# Your code here

Need a hint?

Use the keyword actor followed by the name Counter. Inside curly braces, declare var value = 0.

2

Add an increment function inside the actor

Inside the Counter actor, add a function named increment() that adds 1 to the value variable.

Swift

actor Counter {
    var value = 0
    // Add increment() function here
    // Your code here
}

Need a hint?

Define a function increment() inside the actor that increases value by 1 using value += 1.

3

Create an instance of the actor

Create a constant named myCounter and set it to a new instance of the Counter actor.

Swift

actor Counter {
    var value = 0
    func increment() {
        value += 1
    }
}

// Create myCounter instance here
// Your code here

Need a hint?

Use let myCounter = Counter() to create the actor instance.

4

Call increment and print the value

Call the increment() function on myCounter using await, then print the current value from myCounter also using await.

Swift

actor Counter {
    var value = 0
    func increment() {
        value += 1
    }
}

let myCounter = Counter()

// Call increment and print value below
// Your code here

Need a hint?

Use await myCounter.increment() to call the function, then let currentValue = await myCounter.value to get the value, and finally print(currentValue).