Swift 3中的错误处理

enum NetworkError: Error {
    case invalidURL
    case requestFailed
    case unknownError
}

enum NetworkError: Error {
    case invalidURL
    case requestFailed
    case unknownError
}

func fetchData(from urlString: String) throws -> Data {
    guard let url = URL(string: urlString) else {
        throw NetworkError.invalidURL
    }
    
    let data = try Data(contentsOf: url)
    return data
}

do {
    let data = try fetchData(from: "https://example.com/data.json")
    print("Data fetched successfully: \(data)")
} catch NetworkError.invalidURL {
    print("Invalid URL provided.")
} catch NetworkError.requestFailed {
    print("Failed to fetch data from the server.")
} catch {
    print("An unknown error occurred: \(error)")
}