As I dive deeper into Swift and modern concurrency, I realized how crucial understanding callbacks and completion handlers is for writing robust and clean code. While both seem similar, hereβs a quick differentiation:
PermalinkWhat are Callbacks?
Callbacks are functions passed as arguments to another function and executed later. Theyβre versatile and can be used for both synchronous and asynchronous tasks.
πΉ Example:
func calculate(a: Int, b: Int, callback: (Int) -> Void) {
let result = a + b
callback(result)
}
calculate(a: 3, b: 5) { sum in
print("Sum: \(sum)") // Sum: 8
}
PermalinkWhat about Completion Handlers?
Completion handlers are a specific type of callback used in asynchronous tasks to signal the end of an operation, often returning a result or an error.
πΉ Example:
func fetchData(completion: @escaping (String) -> Void) {
DispatchQueue.global().async {
sleep(2)
DispatchQueue.main.async {
completion("Data fetched")
}
}
}
fetchData { result in
print(result) // Data fetched
}
PermalinkKey Differences Between Callbacks and Completion Handlers:
Aspect | Callback | Completion Handler |
Definition | A general term for passing functions as arguments. | A type of callback used to signal task completion. |
Typical Usage | Synchronous or asynchronous operations. | Specifically for asynchronous tasks (e.g., APIs). |
Focus | Flexible; can be used for intermediate or final steps. | Always indicates the end of a task. |
Error Handling | Error handling is optional. | Often uses the Result type or optional error. |
Terminology | Broader programming concept. | Specific to task completion, commonly used in Swift. |
This understanding bridges the gap between writing basic Swift code and creating scalable, high-performance apps. π»
π‘ Pro Tip: Whether using callbacks or completion handlers, ensure you handle errors and always execute UI updates on the main thread!