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What's async/await? When would you use it?

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Anonymous

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Async/await is a syntax in Swift (and many other programming languages) used for writing asynchronous, non-blocking code in a more readable and linear manner.
  • Async: Marks a function as asynchronous, meaning it can suspend its execution and wait for a result without blocking the thread.
  • Await: Pauses the execution of the async function until the awaited asynchronous operation completes.

When to use it:

  1. Network Calls: For handling API requests or database operations without freezing the UI.
  2. Concurrency: When you want to perform multiple tasks simultaneously but in a structured way.
  3. Simplified Code: To replace nested closures or completion handlers, making the code cleaner and easier to maintain.
Example in Swift:
swiftCopy codefunc fetchData() async throws -> Data {

    let url = URL(string: "https://api.example.com/data")!

    let (data, _) = try await URLSession.shared.data(from: url)

    return data

}
This makes asynchronous code behave more like synchronous code while remaining efficient and non-blocking.
  • What's async/await? When would you use it?
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  • How would you run things asynchronously in an iOS app?
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Interview question asked to iOS Engineers interviewing at Myntra, Asana, Amazon and others: What's async/await? When would you use it?.