Understanding Swift async/await

Introduction

Swift's async/await makes asynchronous code readable and maintainable. In this post, we'll explore the basics and common patterns.

Why async/await?

Before async/await, we used completion handlers and callbacks. The result was often "callback hell" — nested closures that were hard to follow.

With async/await, you write async code that looks like synchronous code:

func fetchUser() async throws -> User {
    let data = try await URLSession.shared.data(from: url)
    return try JSONDecoder().decode(User.self, from: data.0)
}

Key Concepts

• async — Marks a function that can suspend
• await — Suspends until the async operation completes
• Task — Creates a new async context

Error Handling

do {
    let user = try await fetchUser()
    print(user.name)
} catch {
    print("Failed to fetch: \(error)")
}

Next Steps

1. Convert your completion-handler code to async/await
2. Learn about actors for thread-safe state
3. Explore structured concurrency with TaskGroup

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Want to go deeper? Check out our Swift Concurrency course.