Working with Error Handling in Swift

Error handling is an essential part of any programming language, including Swift. It allows you to handle and recover from errors or unexpected conditions that may occur during the execution of your code. Swift provides a robust error handling mechanism through the use of do-catch statements.

In Swift, errors are represented by types that conform to the Error protocol. You can define your custom error types by creating enumerations, structures, or classes that conform to this protocol. Let's take a look at an example:

enum NetworkError: Error {
    case noConnection
    case invalidResponse
}

func fetchData(completion: (Result) -> Void) {
    // Simulating an asynchronous network call
    DispatchQueue.global().async {
        // Assuming some error occurred
        completion(.failure(.noConnection))
    }
}

// Usage
fetchData { result in
    switch result {
    case .success(let data):
        // Process fetched data
    case .failure(let error):
        switch error {
        case .noConnection:
            print("No internet connection.")
        case .invalidResponse:
            print("Invalid server response.")
        }
    }
}

In the above example, we define a custom error type called `NetworkError`, which represents errors that can occur during a network operation. The `fetchData` function simulates an asynchronous network call and takes a completion closure as a parameter. Inside the closure, we return a `Result` type with either a success case containing the fetched data or a failure case with an associated error of type `NetworkError`.

When calling the `fetchData` function, we handle the result using a switch statement to check whether the fetch operation was successful or resulted in an error. If it's an error, we further switch on the specific error type to perform error-specific actions, such as printing relevant error messages.

By using do-catch statements, you can also handle errors that are thrown from functions using the `throw` keyword. This allows you to catch and respond to different types of errors at appropriate levels in your code hierarchy.

Overall, error handling is crucial for writing robust and reliable code in Swift. It helps you gracefully handle exceptional scenarios and recover from errors without crashing your application.

Subject: Error Handling