How should I expose errors from libraries to app layers?

Exposing Errors from Libraries to App Layers in Swift

When working with libraries in Swift, managing errors effectively is crucial for maintaining a robust application. Proper error handling not only aids in debugging but also enhances the user experience by providing meaningful feedback when something goes wrong.

Strategies for Exposing Errors

• Custom Error Types: Define your own error types that conform to the Error protocol. This allows you to create descriptive and specific errors tailored to your library's needs.
• Documentation: Ensure that your functions and methods clearly document the types of errors they can throw. This will help developers understand how to handle these errors at the app layer.
• Result Type: Instead of throwing errors, consider using a Result type, which encapsulates either a success or a failure. This can simplify error handling at the app layer.

Example Implementation

Below is an example of how to define a custom error type and expose it from a library to the app layer:

        // Define a custom error type
        enum LibraryError: Error {
            case networkError
            case decodingError
            case unknownError
        }
        
        // A function that can throw errors
        func fetchData() throws {
            // Simulate an error
            let isError = true // Simulate an error condition
            if isError {
                throw LibraryError.networkError
            }
            // Fetch data logic here
        }
        
        // Usage in app layer
        do {
            try fetchData()
        } catch LibraryError.networkError {
            print("Handle network error")
        } catch {
            print("An unknown error occurred: \(error)")
        }