How to Detect Network Connectivity in iOS

import UIKit
 
class ViewController: UIViewController {
 
    // MARK: - IBOutlets
    @IBOutlet private weak var connectivityStatusContainer: UIView!
    @IBOutlet private weak var connectivityStatus: UILabel! // Connectivity Status Label
 
    @IBOutlet private weak var requestContainer: UIView!
    @IBOutlet private weak var requestContainerInstruction: UILabel! // Connectivity Instructions
    @IBOutlet private weak var requestContainerButton: UIButton! // Request Data Button
 
 
    override func viewDidLoad() {
        super.viewDidLoad()
 
        // Add outline to our views for visibility
        connectivityStatusContainer.addShadow()
        requestContainer.addShadow()
 
        // Instruct the NetworkManagerDelegate that ViewController conforms to the protocol.
        NetworkManager.shared.delegate = self
 
        // Set the initial connectivityStatus before a request is made.
        connectivityStatus.text = "Connection Status: Unknown"
    }
 
 
    @IBAction private func requestDataTapped() {  // IBAction for Request Data Button
        connectivityStatus.text = "Connection Status: Checking"
        NetworkManager.shared.getRequest()
    }
}
 
extension ViewController: NetworkManagerDelegate {
    // Success response that uses the response tuple to set the connectivity status and instruction.
    func networkFinishedWithData(response: (String, String, [String : AnyObject])) {
        DispatchQueue.main.async { [weak self] in
            self?.connectivityStatus.text = "Connection Status: \(response.0)"
            self?.requestContainerInstruction.text = response.1
        }
    }
    // Error response that uses the response tuple to set the connectivity status and instruction.
    func networkFinishedWithError(response: (String, String, [String : AnyObject])) {
        DispatchQueue.main.async { [weak self] in
            self?.connectivityStatus.text = "Connection Status: \(response.0)"
            self?.requestContainerInstruction.text = response.1
        }
    }
 
}

import Foundation
 
 
protocol NetworkManagerDelegate: class {
 
    func networkFinishedWithData(response: (String, String, [String: AnyObject]))
    func networkFinishedWithError(response: (String, String, [String: AnyObject]))
}

import Foundation
 
 
 
class NetworkManager: NSObject {
 
 
    //
    // MARK: - Static Class Constants
    //
    static let shared = NetworkManager()
 
    //
    // MARK: - Variables and Properties
    //
    weak var delegate: NetworkManagerDelegate?
 
    //
    // MARK: - Public constants
    //
    public let urlConfiguration = URLSessionConfiguration.default  // (1) Request Setup or Execution
    public let getSampleURL = "https://httpbin.org/get?arg1=1&arg2=2" // (1) Request Setup or Execution
 
}
 
 
//
// MARK: - Network Manager Extension for Single Requests
//
extension NetworkManager {
 
 
    func getRequest() {
 
        guard let getURL = URL(string: getSampleURL) else {
            return
        }
 
        var getRequest = URLRequest(url: getURL)  // (1) Request Setup or Execution
        getRequest.httpMethod = "GET"
 
        let urlSession = URLSession(configuration: urlConfiguration) // (1) Request Setup or Execution
 
        // Send the GET dataTask here
        let getRequestTask = urlSession.dataTask(with: getRequest, completionHandler: { [weak self] (data, response, error) in
 
            // Ensure that an error is not present, otherwise, return the error along with the message
            if let networkError = error {  // (2) Response Error Processing
                self?.delegate?.networkFinishedWithError(response: NetworkResponse.getNetworkResonse(networkResponse: .networkError,
                                                                                                    error: networkError))
                return
            }
 
            // Perform the JSONSerialization and send back data as long as the statusCode is good
            do {
                if let networkData = data, networkData.count > 0,
                    let networkJSON = try JSONSerialization.jsonObject(with: networkData, options: []) as? [String: AnyObject] {
 
                    // Send back the network Server error response here
                    if let httpResponse = response as? HTTPURLResponse,
                        httpResponse.statusCode >= 500 {
                        // (2) Response Error Processing
                        let error: NSError = NSError(domain: "", code: 0, userInfo: [NSLocalizedDescriptionKey : "Sever Error"])
                        self?.delegate?.networkFinishedWithError(response: NetworkResponse.getNetworkResponse(networkResponse: .networkError,
                                                                                                            data: networkJSON,
                                                                                                            error: error))
                        return
                    }
 
                    // (3) Response Success Processing
                    self?.delegate?.networkFinishedWithData(response: NetworkResponse.getNetworkResponse(networkResponse: .networkData,
                                                                                                       data: networkJSON,
                                                                                                       error: error))
                    return
 
                }
            } catch _ as NSError {
                // Do something with the error here.
            }
            // (2) Response Error Processing
            // Send back a failure.  In this case the JSON would fail to parse to [String: AnyObject]
            self?.delegate?.networkFinishedWithError(response: NetworkResponse.getNetworkResponse(networkResponse: .networkError,
                                                                                                error: error))
 
        })
        getRequestTask.resume() // (1) Request Setup or Execution
 
    }
 
}

import Foundation
 
 
enum NetworkResponse: String {
 
    case networkData
    case networkError
 
    // This is an example for the NetworkConnectivity Turorial.
    // In a real life situation, the enum could be further built out to display actual objects being passed back insted of [String: AnyObject].
    // This would also be an excellent opportunity to use Codables.
    static func getNetworkResponse(networkResponse: NetworkResponse, data: [String: AnyObject] = [:], error: Error?) -> (String, String, [String: AnyObject]) {
 
        switch networkResponse {
 
        case .networkData:
            return (
                "Online",
                "Based upon your last network request, you connectivity is good.",
                data
            )
        case .networkError:
 
            var connectionStatus = "Online"
            var errorInstuction = error?.localizedDescription ?? "Failed to Parse JSON"
 
            if let nsError = error as NSError? {
                let errorCode = nsError.code
                /// -1009 is the offline error code
                /// HTTP load failed (error code: -1009)
                if errorCode == -1009 {
                    connectionStatus = "Offline"
                    errorInstuction = "Please check your internet connection and try your request again."
                }
            }
            return (
                connectionStatus,
                errorInstuction,
                data
            )
 
        }
 
    }
}