Networking

NetworkClient.swift

import Foundation

public enum HTTPMethod: String {
    case get = "GET"
    case post = "POST"
    case put = "PUT"
    case delete = "DELETE"
}

public enum NetworkError: Error {
    case noData
    case notFound
    case serverError
    case unknownError
}

public final class NetworkClient {
    private let urlSession: URLSession
    
    public init(urlSession: URLSession = URLSession(configuration: .default)) {
        self.urlSession = urlSession
    }

    public func makeRequest(to url: URL,
                     method httpMethod: HTTPMethod,
                     body: Data? = nil,
                     headers: [String: String] = [:],
                     completionHandler: @escaping (Result<Data, Error>) -> Void) {
        
        let mutableRequest = NSMutableURLRequest(url: url)
        
        // Set the http method
        mutableRequest.httpMethod = httpMethod.rawValue
                
        // `httpBody` *must* be the last property that we set because of this bug: https://bugs.swift.org/browse/SR-6687
        mutableRequest.httpBody = body
        
        setHeaders(headers, for: mutableRequest)
        
        let task = urlSession.dataTask(with: url) { (data: Data?,
                                                     response: URLResponse?,
                                                     error: Error?) in
            
            guard let httpResponse = response as? HTTPURLResponse else {
                completionHandler(.failure(NetworkError.notFound))
                return
            }
            
            guard let responseData = data else {
                completionHandler(.failure(NetworkError.noData))
                return
            }
            
            // Handle the response
            switch httpResponse.statusCode {
            // Success! Now try to decode the response
            case 200...399:
                completionHandler(.success(responseData))

            // Client error
            case 400...499:
                completionHandler(.failure(NetworkError.notFound))
                
            // Server error
            case 500...599:
                completionHandler(.failure(NetworkError.serverError))
                
            default:
                // This should never happen.
                assertionFailure("Unexpected response code.")
                completionHandler(.failure(NetworkError.unknownError))
            }
        }
        
        task.resume()
    }
    
    private func setHeaders(_ headers: [String: String], for request: NSMutableURLRequest) {
        let standardHeaders = [
            "Accept": "application/json",
            "Accept-Charset": "UTF-8",
            "Accept-Encoding": "gzip"
        ]
        standardHeaders.forEach { request.setValue($1, forHTTPHeaderField: $0) }
        headers.forEach { request.setValue($1, forHTTPHeaderField: $0) }
    }
}

Network Client

This is a very simple networking API. I use it for small programs and interviews.

let networkClient = NetworkClient()
let url = URL("https://github.com")!

networkClient.makeRequest(to: url, method: .get) { result in
  switch result {
    case .sucess:
      print ("It worked!")
    case .failure:
      print ("It didn't")
  }
}