Returning value from async function in swift using async await

Asynchronous programming is a critical part of modern programming, especially for iOS app development. Swift has introduced several new features to support asynchronous programming. One such feature is the ability to define and call asynchronous functions.

When working with asynchronous functions, it’s common to need to return values from them. In this article, we’ll explore how to return values from an async function in Swift.

Defining an Async Function

To define an async function in Swift, we use the async keyword. Here’s an example of a simple async function that returns an integer:

func asyncFunction() async -> Int {
    // some asynchronous code here
    return 42
}

Note that the function signature includes the async keyword and the return type is a Task<Int>.

Returning Values from an Async Function

To return a value from an async function, we need to use the await keyword. The await keyword is used to wait for the result of an asynchronous function before continuing execution.

Here’s an example of an async function that returns a string:

func asyncFunction() async -> String {
    let data = await fetchSomeData()
    return processData(data)
}

In this example, fetchSomeData() is an asynchronous function that returns a value of type Data. We use the await keyword to wait for the result of fetchSomeData() before continuing execution. We then pass the result to processData(), which returns a string.

Handling Errors

When working with asynchronous functions, it’s essential to handle errors that may occur. We can use the throws keyword to indicate that an async function may throw an error.

Here’s an example of an async function that throws an error:

func asyncFunction() async throws -> String {
    let data = try await fetchSomeData()
    return processData(data)
}

In this example, fetchSomeData() may throw an error. We use the try keyword to indicate that we’re calling a function that may throw an error. We then use the await keyword to wait for the result of fetchSomeData().

Conclusion

In this article, we’ve explored how to return values from an async function in Swift. By using the await keyword, we can wait for the result of an asynchronous function before continuing execution. We’ve also seen how to handle errors that may occur when working with async functions.

Remember that async functions are a powerful tool in Swift for building performant and responsive apps. With a solid understanding of async programming in Swift, you’ll be able to write efficient and reliable code that scales with your app.