What are completion handlers in iOS and how do I use them?

What are completion handlers in iOS and how do I use them?

Completion handlers are closures that you pass as arguments to asynchronous functions. They allow you to execute code after a task is completed.

Can you give me an example of how to implement a completion handler?

Sure! Here's a simple example:

func fetchData(completion: @escaping (Data?) -> Void) {
    // Simulate a network call
    DispatchQueue.global().async {
        let data = Data() // Assume we fetched some data
        completion(data)
    }
}

fetchData { data in
    print("Data received: \(data)")
}

What does the @escaping keyword mean in this context?

The @escaping keyword indicates that the closure can outlive the function call, meaning it can be called after the function has returned.

Are there any common mistakes to avoid when using completion handlers?

Yes, common mistakes include forgetting to call the completion handler, causing memory leaks, and not handling errors properly.