2020-02-01-Swift-Reachability

struct SomeStructure {
  func someFunction() {
    // if internet available proceed else return
    guard InternetChecker.shared.internetIsAvailable else { return }
    // do something when internet is available.
  }

Source files are as follows.

InternetChecker.swift

public enum InternetError: Error {
  case noInternet
}

public struct InternetChecker {
  private init() {}

  public static var shared = InternetChecker()

  public var internetIsAvailable: Bool {
    let status = Reach().connectionStatus()
    switch status {
      case .unknown, .offline:
        return false
      case .online(.wwan):
        return true
      case .online(.wiFi):
        return true
    }
  }
}

Reach.swift

import Foundation
import SystemConfiguration


let ReachabilityStatusChangedNotification = "ReachabilityStatusChangedNotification"

enum ReachabilityType: CustomStringConvertible {
  case wwan
  case wiFi

  var description: String {
    switch self {
    case .wwan: return "WWAN"
    case .wiFi: return "WiFi"
    }
  }
}

enum ReachabilityStatus: CustomStringConvertible  {
  case offline
  case online(ReachabilityType)
  case unknown

  var description: String {
    switch self {
    case .offline: return "Offline"
    case .online(let type): return "Online (\(type))"
    case .unknown: return "Unknown"
    }
  }
}

public class Reach {

  func connectionStatus() -> ReachabilityStatus {
    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
    zeroAddress.sin_family = sa_family_t(AF_INET)

    guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
      $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
        SCNetworkReachabilityCreateWithAddress(nil, $0)
      }
    }) else {
      return .unknown
    }

    var flags : SCNetworkReachabilityFlags = []
    if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
      return .unknown
    }

    return ReachabilityStatus(reachabilityFlags: flags)
  }


  func monitorReachabilityChanges() {
    let host = "google.com"
    var context = SCNetworkReachabilityContext(
      version: 0,
      info: nil,
      retain: nil,
      release: nil,
      copyDescription: nil
    )
    let reachability = SCNetworkReachabilityCreateWithName(nil, host)!

    SCNetworkReachabilitySetCallback(reachability, { (_, flags, _) in
      let status = ReachabilityStatus(reachabilityFlags: flags)
      let notificationName = Notification.Name(rawValue: ReachabilityStatusChangedNotification)
      NotificationCenter.default.post(
        name: notificationName,
        object: nil,
        userInfo: ["Status": status.description]
      )
    }, &context)

    SCNetworkReachabilityScheduleWithRunLoop(
      reachability,
      CFRunLoopGetMain(),
      RunLoop.Mode.common as CFString
    )
  }

}

extension ReachabilityStatus {
  init(reachabilityFlags flags: SCNetworkReachabilityFlags) {
    let connectionRequired = flags.contains(.connectionRequired)
    let isReachable = flags.contains(.reachable)
    let isWWAN = flags.contains(.isWWAN)

    if !connectionRequired && isReachable {
      if isWWAN {
        self = .online(.wwan)
      } else {
        self = .online(.wiFi)
      }
    } else {
      self =  .offline
    }
  }
}