Swift — Type Inference

Basic Result

enum NetworkError: Error {
    case badURL
    case noData
    case decodingFailed
}

func fetchData(from urlString: String) -> Result<String, NetworkError> {
    guard let _ = URL(string: urlString) else {
        return .failure(.badURL)
    }
    return .success("Data loaded")
}

let result = fetchData(from: "https://example.com")
switch result {
case .success(let data): print(data)
case .failure(let error): print(error)
}

Mapping Result

let doubled = result.map { $0.count * 2 }
let transformed = result.flatMap { count in
    // transform
}

Mini Practice

Write Swift code that:

1. Creates a Result type
2. Uses switch to handle result
3. Maps and flatMaps result
4. Creates custom error types

Up Next

In the next lesson, you'll learn about Combine — reactive programming.