Verifique a conexão à Internet com o Swift

Quando tento verificar uma conexão com a Internet no meu iPhone, recebo vários erros. Alguém pode me ajudar a consertar isso?

O código:

import Foundation
import SystemConfiguration

public class Reachability {

class func isConnectedToNetwork() -> Bool {

    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
    zeroAddress.sin_family = sa_family_t(AF_INET)

    let defaultRouteReachability = withUnsafePointer(&zeroAddress) {
        SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
    }

    var flags: SCNetworkReachabilityFlags = 0

    if SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) == 0 {
        return false
    }

    let isReachable = (flags & UInt32(kSCNetworkFlagsReachable)) != 0
    let needsConnection = (flags & UInt32(kSCNetworkFlagsConnectionRequired)) != 0

    return (isReachable && !needsConnection) ? true : false
}

}

Os erros com o código:

Se estiver ilegível, o erro 1 diz:

'Int' não é conversível em 'SCNetworkReachabilityFlags'

Erro 2 e 3:

Não foi possível encontrar uma sobrecarga para 'init' que aceita os argumentos fornecidos

Para resolver o problema 4G mencionado nos comentários, usei a implementação de acessibilidade @AshleyMills como referência e reescrevi a acessibilidade para o Swift 3.1:

atualizado: Xcode 10.1 • Swift 4 ou posterior

Arquivo Reachability.swift

import Foundation
import SystemConfiguration

class Reachability {
    var hostname: String?
    var isRunning = false
    var isReachableOnWWAN: Bool
    var reachability: SCNetworkReachability?
    var reachabilityFlags = SCNetworkReachabilityFlags()
    let reachabilitySerialQueue = DispatchQueue(label: "ReachabilityQueue")
    init(hostname: String) throws {
        guard let reachability = SCNetworkReachabilityCreateWithName(nil, hostname) else {
            throw Network.Error.failedToCreateWith(hostname)
        }
        self.reachability = reachability
        self.hostname = hostname
        isReachableOnWWAN = true
        try start()
    }
    init() throws {
        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
        zeroAddress.sin_family = sa_family_t(AF_INET)
        guard let reachability = withUnsafePointer(to: &zeroAddress, {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                SCNetworkReachabilityCreateWithAddress(nil, $0)
            }
        }) else {
            throw Network.Error.failedToInitializeWith(zeroAddress)
        }
        self.reachability = reachability
        isReachableOnWWAN = true
        try start()
    }
    var status: Network.Status {
        return  !isConnectedToNetwork ? .unreachable :
                isReachableViaWiFi    ? .wifi :
                isRunningOnDevice     ? .wwan : .unreachable
    }
    var isRunningOnDevice: Bool = {
        #if targetEnvironment(simulator)
            return false
        #else
            return true
        #endif
    }()
    deinit { stop() }
}

extension Reachability {

    func start() throws {
        guard let reachability = reachability, !isRunning else { return }
        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = Unmanaged<Reachability>.passUnretained(self).toOpaque()
        guard SCNetworkReachabilitySetCallback(reachability, callout, &context) else { stop()
            throw Network.Error.failedToSetCallout
        }
        guard SCNetworkReachabilitySetDispatchQueue(reachability, reachabilitySerialQueue) else { stop()
            throw Network.Error.failedToSetDispatchQueue
        }
        reachabilitySerialQueue.async { self.flagsChanged() }
        isRunning = true
    }

    func stop() {
        defer { isRunning = false }
        guard let reachability = reachability else { return }
        SCNetworkReachabilitySetCallback(reachability, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachability, nil)
        self.reachability = nil
    }

    var isConnectedToNetwork: Bool {
        return isReachable &&
               !isConnectionRequiredAndTransientConnection &&
               !(isRunningOnDevice && isWWAN && !isReachableOnWWAN)
    }

    var isReachableViaWiFi: Bool {
        return isReachable && isRunningOnDevice && !isWWAN
    }

    /// Flags that indicate the reachability of a network node name or address, including whether a connection is required, and whether some user intervention might be required when establishing a connection.
    var flags: SCNetworkReachabilityFlags? {
        guard let reachability = reachability else { return nil }
        var flags = SCNetworkReachabilityFlags()
        return withUnsafeMutablePointer(to: &flags) {
            SCNetworkReachabilityGetFlags(reachability, UnsafeMutablePointer($0))
            } ? flags : nil
    }

    /// compares the current flags with the previous flags and if changed posts a flagsChanged notification
    func flagsChanged() {
        guard let flags = flags, flags != reachabilityFlags else { return }
        reachabilityFlags = flags
        NotificationCenter.default.post(name: .flagsChanged, object: self)
    }

    /// The specified node name or address can be reached via a transient connection, such as PPP.
    var transientConnection: Bool { return flags?.contains(.transientConnection) == true }

    /// The specified node name or address can be reached using the current network configuration.
    var isReachable: Bool { return flags?.contains(.reachable) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. If this flag is set, the kSCNetworkReachabilityFlagsConnectionOnTraffic flag, kSCNetworkReachabilityFlagsConnectionOnDemand flag, or kSCNetworkReachabilityFlagsIsWWAN flag is also typically set to indicate the type of connection required. If the user must manually make the connection, the kSCNetworkReachabilityFlagsInterventionRequired flag is also set.
    var connectionRequired: Bool { return flags?.contains(.connectionRequired) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. Any traffic directed to the specified name or address will initiate the connection.
    var connectionOnTraffic: Bool { return flags?.contains(.connectionOnTraffic) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established.
    var interventionRequired: Bool { return flags?.contains(.interventionRequired) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. The connection will be established "On Demand" by the CFSocketStream programming interface (see CFStream Socket Additions for information on this). Other functions will not establish the connection.
    var connectionOnDemand: Bool { return flags?.contains(.connectionOnDemand) == true }

    /// The specified node name or address is one that is associated with a network interface on the current system.
    var isLocalAddress: Bool { return flags?.contains(.isLocalAddress) == true }

    /// Network traffic to the specified node name or address will not go through a gateway, but is routed directly to one of the interfaces in the system.
    var isDirect: Bool { return flags?.contains(.isDirect) == true }

    /// The specified node name or address can be reached via a cellular connection, such as EDGE or GPRS.
    var isWWAN: Bool { return flags?.contains(.isWWAN) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. If this flag is set
    /// The specified node name or address can be reached via a transient connection, such as PPP.
    var isConnectionRequiredAndTransientConnection: Bool {
        return (flags?.intersection([.connectionRequired, .transientConnection]) == [.connectionRequired, .transientConnection]) == true
    }
}

func callout(reachability: SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutableRawPointer?) {
    guard let info = info else { return }
    DispatchQueue.main.async {
        Unmanaged<Reachability>
            .fromOpaque(info)
            .takeUnretainedValue()
            .flagsChanged()
    }
}

extension Notification.Name {
    static let flagsChanged = Notification.Name("FlagsChanged")
}

struct Network {
    static var reachability: Reachability!
    enum Status: String {
        case unreachable, wifi, wwan
    }
    enum Error: Swift.Error {
        case failedToSetCallout
        case failedToSetDispatchQueue
        case failedToCreateWith(String)
        case failedToInitializeWith(sockaddr_in)
    }
}

Uso

Inicialize-o no método AppDelegate.swift didFinishLaunchingWithOptions e lide com os erros que possam ocorrer:

import UIKit
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        do {
            try Network.reachability = Reachability(hostname: "www.google.com")
        }
        catch {
            switch error as? Network.Error {
            case let .failedToCreateWith(hostname)?:
                print("Network error:\nFailed to create reachability object With host named:", hostname)
            case let .failedToInitializeWith(address)?:
                print("Network error:\nFailed to initialize reachability object With address:", address)
            case .failedToSetCallout?:
                print("Network error:\nFailed to set callout")
            case .failedToSetDispatchQueue?:
                print("Network error:\nFailed to set DispatchQueue")
            case .none:
                print(error)
            }
        }
        return true
    }
}

E uma amostra do controlador de exibição:

import UIKit
class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        NotificationCenter.default
            .addObserver(self,
                         selector: #selector(statusManager),
                         name: .flagsChanged,
                         object: nil)
        updateUserInterface()
    }
    func updateUserInterface() {
        switch Network.reachability.status {
        case .unreachable:
            view.backgroundColor = .red
        case .wwan:
            view.backgroundColor = .yellow
        case .wifi:
            view.backgroundColor = .green
        }
        print("Reachability Summary")
        print("Status:", Network.reachability.status)
        print("HostName:", Network.reachability.hostname ?? "nil")
        print("Reachable:", Network.reachability.isReachable)
        print("Wifi:", Network.reachability.isReachableViaWiFi)
    }
    @objc func statusManager(_ notification: Notification) {
        updateUserInterface()
    }
}

Projeto de exemplo

Para Swift 3, Swift 4 (trabalhando com celular e Wi-Fi):

import SystemConfiguration

public class Reachability {

    class func isConnectedToNetwork() -> Bool {

        var zeroAddress = sockaddr_in(sin_len: 0, sin_family: 0, sin_port: 0, sin_addr: in_addr(s_addr: 0), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
        zeroAddress.sin_len = UInt8(MemoryLayout.size(ofValue: zeroAddress))
        zeroAddress.sin_family = sa_family_t(AF_INET)

        let defaultRouteReachability = withUnsafePointer(to: &zeroAddress) {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {zeroSockAddress in
                SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
            }
        }

        var flags: SCNetworkReachabilityFlags = SCNetworkReachabilityFlags(rawValue: 0)
        if SCNetworkReachabilityGetFlags(defaultRouteReachability!, &flags) == false {
            return false
        }

        /* Only Working for WIFI
        let isReachable = flags == .reachable
        let needsConnection = flags == .connectionRequired

        return isReachable && !needsConnection
        */

        // Working for Cellular and WIFI
        let isReachable = (flags.rawValue & UInt32(kSCNetworkFlagsReachable)) != 0
        let needsConnection = (flags.rawValue & UInt32(kSCNetworkFlagsConnectionRequired)) != 0
        let ret = (isReachable && !needsConnection)

        return ret

    }
}

Uso:

if Reachability.isConnectedToNetwork(){
    print("Internet Connection Available!")
}else{
    print("Internet Connection not Available!")
}

Crie um novo arquivo Swift dentro do seu projeto, nomeie-o Reachability.swift. Recorte e cole o código a seguir para criar sua classe.

import Foundation
import SystemConfiguration

public class Reachability {

    class func isConnectedToNetwork() -> Bool {

        var zeroAddress = sockaddr_in(sin_len: 0, sin_family: 0, sin_port: 0, sin_addr: in_addr(s_addr: 0), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
        zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
        zeroAddress.sin_family = sa_family_t(AF_INET)

        let defaultRouteReachability = withUnsafePointer(&zeroAddress) {
            SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, UnsafePointer($0))
        }

        var flags: SCNetworkReachabilityFlags = SCNetworkReachabilityFlags(rawValue: 0)
        if SCNetworkReachabilityGetFlags(defaultRouteReachability!, &flags) == false {
             return false
        }

        let isReachable = flags == .Reachable
        let needsConnection = flags == .ConnectionRequired

        return isReachable && !needsConnection

    }
}

Você pode verificar a conexão à Internet em qualquer lugar do seu projeto usando este código:

if Reachability.isConnectedToNetwork() {
    println("Internet connection OK")
} else {
    println("Internet connection FAILED")
}

Se o usuário não estiver conectado à Internet, você poderá exibir uma caixa de diálogo de alerta para notificá-lo.

if Reachability.isConnectedToNetwork() {
    println("Internet connection OK")
} else {
    println("Internet connection FAILED")
    var alert = UIAlertView(title: "No Internet Connection", message: "Make sure your device is connected to the internet.", delegate: nil, cancelButtonTitle: "OK")
    alert.show()
}

Explicação:

Estamos criando uma classe pública reutilizável e um método que pode ser usado em qualquer lugar do projeto para verificar a conectividade com a Internet. Exigimos a adição das estruturas Foundation e System Configuration.

Na classe pública de alcançabilidade, o método isConnectedToNetwork() -> Bool { }retornará um valor booleano sobre conectividade à Internet. Usamos um loop if para executar as ações necessárias no caso. Espero que isso seja suficiente. Felicidades!

Se alguém já estiver usando o Alamofire, então -

struct Connectivity {
  static let sharedInstance = NetworkReachabilityManager()!
  static var isConnectedToInternet:Bool {
      return self.sharedInstance.isReachable
    }
}

Uso:

if Connectivity.isConnectedToInternet {
     print("Connected")
 } else {
     print("No Internet")
}

Fiz uma verificação da implementação da classe de acessibilidade de Ashley Mill sem o Cocoa Pods / Dependancy Manager. A idéia é liberar a dependência de acessibilidade no projeto.

Xcode 7.2 - Swift 2.1

1) https://github.com/ashleymills/Reachability.swift . O download adiciona a classe de alcançabilidade ao projeto.

Nota: Ao adicionar, verifique se 'copiar itens se necessário' está marcado.

2) Faça uma classe AppManager.swift. Esta classe atenderá como classe de Modelo Público, onde métodos e dados públicos serão adicionados e podem ser utilizados em qualquer VC.

//  AppManager.swift

import UIKit
import Foundation

class AppManager: NSObject{
    var delegate:AppManagerDelegate? = nil
    private var _useClosures:Bool = false
    private var reachability: Reachability?
    private var _isReachability:Bool = false
    private var _reachabiltyNetworkType :String?

    var isReachability:Bool {
        get {return _isReachability}
    }  
   var reachabiltyNetworkType:String {
    get {return _reachabiltyNetworkType! }
   }   




    // Create a shared instance of AppManager
    final  class var sharedInstance : AppManager {
        struct Static {
            static var instance : AppManager?
        }
        if !(Static.instance != nil) {
            Static.instance = AppManager()

        }
        return Static.instance!
    }

    // Reachability Methods
    func initRechabilityMonitor() {
        print("initialize rechability...")
        do {
            let reachability = try Reachability.reachabilityForInternetConnection()
            self.reachability = reachability
        } catch ReachabilityError.FailedToCreateWithAddress(let address) {
            print("Unable to create\nReachability with address:\n\(address)")
            return
        } catch {}
        if (_useClosures) {
            reachability?.whenReachable = { reachability in
                self.notifyReachability(reachability)
            }
            reachability?.whenUnreachable = { reachability in
                self.notifyReachability(reachability)
            }
        } else {
            self.notifyReachability(reachability!)
        }

        do {
            try reachability?.startNotifier()
        } catch {
            print("unable to start notifier")
            return
        }


    }        
    private func notifyReachability(reachability:Reachability) {
        if reachability.isReachable() {
            self._isReachability = true

//Determine Network Type 
      if reachability.isReachableViaWiFi() {   
        self._reachabiltyNetworkType = CONNECTION_NETWORK_TYPE.WIFI_NETWORK.rawValue
      } else {
        self._reachabiltyNetworkType = CONNECTION_NETWORK_TYPE.WWAN_NETWORK.rawValue
      }

        } else {
            self._isReachability = false
self._reachabiltyNetworkType = CONNECTION_NETWORK_TYPE.OTHER.rawValue

        }

        NSNotificationCenter.defaultCenter().addObserver(self, selector: "reachabilityChanged:", name: ReachabilityChangedNotification, object: reachability)
    }
    func reachabilityChanged(note: NSNotification) {
        let reachability = note.object as! Reachability
        dispatch_async(dispatch_get_main_queue()) {
            if (self._useClosures) {
                self.reachability?.whenReachable = { reachability in
                    self.notifyReachability(reachability)
                }
                self.reachability?.whenUnreachable = { reachability in
                    self.notifyReachability(reachability)
                }
            } else {
                self.notifyReachability(reachability)
            }
            self.delegate?.reachabilityStatusChangeHandler(reachability)
        }
    }
    deinit {
        reachability?.stopNotifier()
        if (!_useClosures) {
            NSNotificationCenter.defaultCenter().removeObserver(self, name: ReachabilityChangedNotification, object: nil)
        }
    }
}

3) Faça uma classe de delegado. Eu uso o método delegado para notificar o status da conectividade.

//  Protocols.swift

import Foundation
@objc protocol AppManagerDelegate:NSObjectProtocol {

    func reachabilityStatusChangeHandler(reachability:Reachability)
}

4) Faça a classe Parent de UIViewController (método de herança). A classe pai possui métodos acessíveis a todos os VCs filhos.

//  UIappViewController.swift

    import UIKit

    class UIappViewController: UIViewController,AppManagerDelegate {
        var manager:AppManager = AppManager.sharedInstance

        override func viewDidLoad() {
            super.viewDidLoad()
            manager.delegate = self
        }
        override func didReceiveMemoryWarning() {
            super.didReceiveMemoryWarning()
        }
        func reachabilityStatusChangeHandler(reachability: Reachability) {
            if reachability.isReachable() {
                print("isReachable")
            } else {
                print("notReachable")
            }
        }
    }

5) Inicie o Monitoramento de conectividade à Internet em tempo real no AppDelegate.

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    AppManager.sharedInstance.initRechabilityMonitor()
return true
}

6) Adicionei um AppReference de nome de arquivo Swift para armazenar valores de enumeração constantes.

//  AppReference.swift

import Foundation

enum CONNECTION_NETWORK_TYPE : String {

  case WIFI_NETWORK = "Wifi"
  case WWAN_NETWORK = "Cellular"
  case OTHER = "Other"

}

7) No ViewController (por exemplo, você deseja chamar uma API apenas se a rede estiver disponível)

//  ViewController.swift

        import UIKit

class ViewController: UIappViewController {
  var reachability:Reachability?

  override func viewDidLoad() {
    super.viewDidLoad()
    manager.delegate = self

    if(AppManager.sharedInstance.isReachability)
    {
      print("net available")
      //call API from here.

    } else {
      dispatch_async(dispatch_get_main_queue()) {
        print("net not available")
        //Show Alert
      }
    }


    //Determine Network Type
    if(AppManager.sharedInstance.reachabiltyNetworkType == "Wifi")
    {
      print(".Wifi")
    }
    else if (AppManager.sharedInstance.reachabiltyNetworkType == "Cellular")
    {
      print(".Cellular")
    }
    else {
      dispatch_async(dispatch_get_main_queue()) {
        print("Network not reachable")
      }
    }

  }
  override func viewWillAppear(animated: Bool) {
  }
  override func didReceiveMemoryWarning() {
  }
}

O exemplo pode ser baixado em https://github.com/alvinreuben/Reachability-Sample

Atualizado para o Swift 3.1- https://github.com/alvinvgeorge/Reachability-UpgradedToSwift3

A Apple introduziu o Network Framework no iOS12.

import Foundation
import Network

class NetworkReachability {

   var pathMonitor: NWPathMonitor!
   var path: NWPath?
   lazy var pathUpdateHandler: ((NWPath) -> Void) = { path in
    self.path = path
    if path.status == NWPath.Status.satisfied {
        print("Connected")
    } else if path.status == NWPath.Status.unsatisfied {
        print("unsatisfied")
    } else if path.status == NWPath.Status.requiresConnection {
        print("requiresConnection")
    } 
}

let backgroudQueue = DispatchQueue.global(qos: .background)

init() {
    pathMonitor = NWPathMonitor()
    pathMonitor.pathUpdateHandler = self.pathUpdateHandler
    pathMonitor.start(queue: backgroudQueue)
   } 

 func isNetworkAvailable() -> Bool {
        if let path = self.path {
           if path.status == NWPath.Status.satisfied {
            return true
          }
        }
       return false
   }
 }

Use isso para o Swift-5 +

import Foundation
import UIKit
import SystemConfiguration

public class InternetConnectionManager {


    private init() {

    }

    public static func isConnectedToNetwork() -> Bool {

        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout.size(ofValue: zeroAddress))
        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 false
        }
        var flags = SCNetworkReachabilityFlags()
        if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
            return false
        }
        let isReachable = (flags.rawValue & UInt32(kSCNetworkFlagsReachable)) != 0
        let needsConnection = (flags.rawValue & UInt32(kSCNetworkFlagsConnectionRequired)) != 0
        return (isReachable && !needsConnection)
    }

}

Uso:

InternetConnectionManager.isConnectedToNetwork{
    print("Connected")
}else{
    print("Not Connected")
}

Ou basta usar isso frameworkpara maisUtilities : Link

Só descobri isso por mim mesmo.

Xcode: 7.3.1, iOS 9.3.3

Usando ashleymills / Reachability.swift como Reachability.swift no meu projeto, criei a seguinte função:

func hasConnectivity() -> Bool {
    do {
        let reachability: Reachability = try Reachability.reachabilityForInternetConnection()
        let networkStatus: Int = reachability.currentReachabilityStatus.hashValue

        return (networkStatus != 0)
    }
    catch {
        // Handle error however you please
        return false
    }
}

Basta ligar para hasConnectivity()onde você precisar verificar a conexão. Isso funciona tanto para Wifi quanto para celular.

Adicionando o Reachability.swift do ashleymills para que as pessoas não precisem se mover entre sites:

Copyright (c) 2014, Ashley Mills
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/

// Reachability.swift version 2.2beta2

import SystemConfiguration
import Foundation

public enum ReachabilityError: ErrorType {
    case FailedToCreateWithAddress(sockaddr_in)
    case FailedToCreateWithHostname(String)
    case UnableToSetCallback
    case UnableToSetDispatchQueue
}

public let ReachabilityChangedNotification = "ReachabilityChangedNotification"

func callback(reachability:SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutablePointer<Void>) {
    let reachability = Unmanaged<Reachability>.fromOpaque(COpaquePointer(info)).takeUnretainedValue()

    dispatch_async(dispatch_get_main_queue()) {
        reachability.reachabilityChanged(flags)
    }
}


public class Reachability: NSObject {

    public typealias NetworkReachable = (Reachability) -> ()
    public typealias NetworkUnreachable = (Reachability) -> ()

    public enum NetworkStatus: CustomStringConvertible {

        case NotReachable, ReachableViaWiFi, ReachableViaWWAN

        public var description: String {
            switch self {
            case .ReachableViaWWAN:
                return "Cellular"
            case .ReachableViaWiFi:
                return "WiFi"
            case .NotReachable:
                return "No Connection"
            }
        }
    }

    // MARK: - *** Public properties ***
    public var whenReachable: NetworkReachable?
    public var whenUnreachable: NetworkUnreachable?
    public var reachableOnWWAN: Bool
    public var notificationCenter = NSNotificationCenter.defaultCenter()

    public var currentReachabilityStatus: NetworkStatus {
        if isReachable() {
            if isReachableViaWiFi() {
                return .ReachableViaWiFi
            }
            if isRunningOnDevice {
                return .ReachableViaWWAN
            }
        }
        return .NotReachable
    }

    public var currentReachabilityString: String {
        return "\(currentReachabilityStatus)"
    }

    private var previousFlags: SCNetworkReachabilityFlags?

    // MARK: - *** Initialisation methods ***

    required public init(reachabilityRef: SCNetworkReachability) {
        reachableOnWWAN = true
        self.reachabilityRef = reachabilityRef
    }

    public convenience init(hostname: String) throws {

        let nodename = (hostname as NSString).UTF8String
        guard let ref = SCNetworkReachabilityCreateWithName(nil, nodename) else { throw ReachabilityError.FailedToCreateWithHostname(hostname) }

        self.init(reachabilityRef: ref)
    }

    public class func reachabilityForInternetConnection() throws -> Reachability {

        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
        zeroAddress.sin_family = sa_family_t(AF_INET)

        guard let ref = withUnsafePointer(&zeroAddress, {
            SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
        }) else { throw ReachabilityError.FailedToCreateWithAddress(zeroAddress) }

        return Reachability(reachabilityRef: ref)
    }

    public class func reachabilityForLocalWiFi() throws -> Reachability {

        var localWifiAddress: sockaddr_in = sockaddr_in(sin_len: __uint8_t(0), sin_family: sa_family_t(0), sin_port: in_port_t(0), sin_addr: in_addr(s_addr: 0), sin_zero: (0, 0, 0, 0, 0, 0, 0, 0))
        localWifiAddress.sin_len = UInt8(sizeofValue(localWifiAddress))
        localWifiAddress.sin_family = sa_family_t(AF_INET)

        // IN_LINKLOCALNETNUM is defined in <netinet/in.h> as 169.254.0.0
        let address: UInt32 = 0xA9FE0000
        localWifiAddress.sin_addr.s_addr = in_addr_t(address.bigEndian)

        guard let ref = withUnsafePointer(&localWifiAddress, {
            SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
        }) else { throw ReachabilityError.FailedToCreateWithAddress(localWifiAddress) }

        return Reachability(reachabilityRef: ref)
    }

    // MARK: - *** Notifier methods ***
    public func startNotifier() throws {

        guard !notifierRunning else { return }

        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = UnsafeMutablePointer(Unmanaged.passUnretained(self).toOpaque())

        if !SCNetworkReachabilitySetCallback(reachabilityRef!, callback, &context) {
            stopNotifier()
            throw ReachabilityError.UnableToSetCallback
        }

        if !SCNetworkReachabilitySetDispatchQueue(reachabilityRef!, reachabilitySerialQueue) {
            stopNotifier()
            throw ReachabilityError.UnableToSetDispatchQueue
        }

        // Perform an intial check
        dispatch_async(reachabilitySerialQueue) { () -> Void in
            let flags = self.reachabilityFlags
            self.reachabilityChanged(flags)
        }

        notifierRunning = true
    }

    public func stopNotifier() {
        defer { notifierRunning = false }
        guard let reachabilityRef = reachabilityRef else { return }

        SCNetworkReachabilitySetCallback(reachabilityRef, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachabilityRef, nil)
    }

    // MARK: - *** Connection test methods ***
    public func isReachable() -> Bool {
        let flags = reachabilityFlags
        return isReachableWithFlags(flags)
    }

    public func isReachableViaWWAN() -> Bool {

        let flags = reachabilityFlags

        // Check we're not on the simulator, we're REACHABLE and check we're on WWAN
        return isRunningOnDevice && isReachable(flags) && isOnWWAN(flags)
    }

    public func isReachableViaWiFi() -> Bool {

        let flags = reachabilityFlags

        // Check we're reachable
        if !isReachable(flags) {
            return false
        }

        // Must be on WiFi if reachable but not on an iOS device (i.e. simulator)
        if !isRunningOnDevice {
            return true
        }

        // Check we're NOT on WWAN
        return !isOnWWAN(flags)
    }

    // MARK: - *** Private methods ***
    private var isRunningOnDevice: Bool = {
        #if (arch(i386) || arch(x86_64)) && os(iOS)
            return false
        #else
            return true
        #endif
    }()

    private var notifierRunning = false
    private var reachabilityRef: SCNetworkReachability?
    private let reachabilitySerialQueue = dispatch_queue_create("uk.co.ashleymills.reachability", DISPATCH_QUEUE_SERIAL)

    private func reachabilityChanged(flags: SCNetworkReachabilityFlags) {

        guard previousFlags != flags else { return }

        if isReachableWithFlags(flags) {
            if let block = whenReachable {
                block(self)
            }
        } else {
            if let block = whenUnreachable {
                block(self)
            }
        }

        notificationCenter.postNotificationName(ReachabilityChangedNotification, object:self)

        previousFlags = flags
    }

    private func isReachableWithFlags(flags: SCNetworkReachabilityFlags) -> Bool {

        if !isReachable(flags) {
            return false
        }

        if isConnectionRequiredOrTransient(flags) {
            return false
        }

        if isRunningOnDevice {
            if isOnWWAN(flags) && !reachableOnWWAN {
                // We don't want to connect when on 3G.
                return false
            }
        }

        return true
    }

    // WWAN may be available, but not active until a connection has been established.
    // WiFi may require a connection for VPN on Demand.
    private func isConnectionRequired() -> Bool {
        return connectionRequired()
    }

    private func connectionRequired() -> Bool {
        let flags = reachabilityFlags
        return isConnectionRequired(flags)
    }

    // Dynamic, on demand connection?
    private func isConnectionOnDemand() -> Bool {
        let flags = reachabilityFlags
        return isConnectionRequired(flags) && isConnectionOnTrafficOrDemand(flags)
    }

    // Is user intervention required?
    private func isInterventionRequired() -> Bool {
        let flags = reachabilityFlags
        return isConnectionRequired(flags) && isInterventionRequired(flags)
    }

    private func isOnWWAN(flags: SCNetworkReachabilityFlags) -> Bool {
        #if os(iOS)
            return flags.contains(.IsWWAN)
        #else
            return false
        #endif
    }
    private func isReachable(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.Reachable)
    }
    private func isConnectionRequired(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.ConnectionRequired)
    }
    private func isInterventionRequired(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.InterventionRequired)
    }
    private func isConnectionOnTraffic(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.ConnectionOnTraffic)
    }
    private func isConnectionOnDemand(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.ConnectionOnDemand)
    }
    func isConnectionOnTrafficOrDemand(flags: SCNetworkReachabilityFlags) -> Bool {
        return !flags.intersect([.ConnectionOnTraffic, .ConnectionOnDemand]).isEmpty
    }
    private func isTransientConnection(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.TransientConnection)
    }
    private func isLocalAddress(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.IsLocalAddress)
    }
    private func isDirect(flags: SCNetworkReachabilityFlags) -> Bool {
        return flags.contains(.IsDirect)
    }
    private func isConnectionRequiredOrTransient(flags: SCNetworkReachabilityFlags) -> Bool {
        let testcase:SCNetworkReachabilityFlags = [.ConnectionRequired, .TransientConnection]
        return flags.intersect(testcase) == testcase
    }

    private var reachabilityFlags: SCNetworkReachabilityFlags {

        guard let reachabilityRef = reachabilityRef else { return SCNetworkReachabilityFlags() }

        var flags = SCNetworkReachabilityFlags()
        let gotFlags = withUnsafeMutablePointer(&flags) {
            SCNetworkReachabilityGetFlags(reachabilityRef, UnsafeMutablePointer($0))
        }

        if gotFlags {
            return flags
        } else {
            return SCNetworkReachabilityFlags()
        }
    }

    override public var description: String {

        var W: String
        if isRunningOnDevice {
            W = isOnWWAN(reachabilityFlags) ? "W" : "-"
        } else {
            W = "X"
        }
        let R = isReachable(reachabilityFlags) ? "R" : "-"
        let c = isConnectionRequired(reachabilityFlags) ? "c" : "-"
        let t = isTransientConnection(reachabilityFlags) ? "t" : "-"
        let i = isInterventionRequired(reachabilityFlags) ? "i" : "-"
        let C = isConnectionOnTraffic(reachabilityFlags) ? "C" : "-"
        let D = isConnectionOnDemand(reachabilityFlags) ? "D" : "-"
        let l = isLocalAddress(reachabilityFlags) ? "l" : "-"
        let d = isDirect(reachabilityFlags) ? "d" : "-"

        return "\(W)\(R) \(c)\(t)\(i)\(C)\(D)\(l)\(d)"
    }

    deinit {
        stopNotifier()

        reachabilityRef = nil
        whenReachable = nil
        whenUnreachable = nil
    }
}

Embora não responda diretamente à sua pergunta, gostaria de mencionar que a Apple recentemente teve esta palestra:

https://developer.apple.com/videos/play/wwdc2018/714/

Por volta das 09:55, ele fala sobre fazer essas coisas que você está perguntando:

1. Verifique a conexão
2. Se conexão -> Faça alguma coisa
3. Se não houver conexão -> Faça outra coisa (aguarde? Tente novamente?)

No entanto, isso tem algumas armadilhas:

• E se no passo 2 ele disser que tem uma conexão, mas 0,5 segundos depois ele não tiver?
• E se o usuário estiver atrás de um proxy
• Por último, mas não menos importante, e se algumas respostas aqui não conseguirem determinar a conectividade, certo? (Tenho certeza de que, se você alternar rapidamente sua conexão, acessar o wi-fi e desligá-lo (apenas torne as coisas complicadas), quase nunca será possível determinar corretamente se eu tenho uma conexão ou não.
• Citação do vídeo: "Não há como garantir se uma operação futura será bem-sucedida ou não"

Os seguintes pontos são algumas práticas recomendadas de acordo com a Apple:

• definido waitsForConnectivitycomo true ( https://developer.apple.com/documentation/foundation/urlsessionconfiguration/2908812-waitsforconnectivity )
• responda ao método delegado taskIsWaitingForConnectivity( https://developer.apple.com/documentation/foundation/urlsessiontaskdelegate/2908819-urlsession ). Esta é a maneira recomendada pela Apple de verificar a conectividade, conforme mencionado no vídeo em 33:25.

De acordo com a palestra, não deve haver nenhum motivo para verificar previamente se você tem conexão com a Internet ou não, pois pode não ser preciso no momento em que você envia sua solicitação ao servidor .

Eu fiz minha própria solução usando NSTimer e Alamofire:

import Alamofire

public class ConnectionHelper: NSObject {
    var request: Alamofire.Request?

    func isInternetConnected(completionHandler: Bool -> Void) {
        NSTimer.scheduledTimerWithTimeInterval(5.0, target: self, selector: "requestTimeout", userInfo: nil, repeats: false)

        request = Alamofire
            .request(
                Method.HEAD,
                "http://www.testurl.com"
            )
            .response { response in
                if response.3?.code == -999 {
                    completionHandler(
                        false
                    )
                } else {
                    completionHandler(
                        true
                    )
                }
        }
    }

    func requestTimeout() {
        request!.cancel()
    }
}

O NSTimer é usado como tempo limite e foi usado devido a resultados não confiáveis ​​usando o tempo limite Alamofire. A solicitação deve ser feita para um URL em que você confia, como seu próprio servidor ou o servidor que hospeda os serviços dos quais você depende.

Quando o cronômetro expira, a solicitação é cancelada e os resultados são retornados usando um manipulador de conclusão.

Uso:

ConnectionHelper().isInternetConnected() { internetConnected in
    if internetConnected {
        // Connected
    } else {
        // Not connected
    }
}

Se você estiver usando o Alamofire, poderá fazer algo assim:

let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
configuration.timeoutIntervalForRequest = 15 //Set timeouts in sec
configuration.timeoutIntervalForResource = 15

let alamoFireManager = Alamofire.Manager(configuration:configuration)
alamoFireManager?.request(.GET, "https://yourURL.com", parameters: headers, encoding: .URL)
                     .validate()
                              .responseJSON { response in

                                if let error = response.result.error {
                                   switch error.code{
                                    case -1001:
                                        print("Slow connection")
                                        return
                                    case -1009:
                                        print("No Connection!")
                                        return
                                    default: break
                                    }
                                }

Swift 5

import SystemConfiguration    

protocol Utilities {}
extension NSObject: Utilities {
    enum ReachabilityStatus {
        case notReachable
        case reachableViaWWAN
        case reachableViaWiFi
    }

    var currentReachabilityStatus: 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 .notReachable
        }

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

        if flags.contains(.reachable) == false {
            // The target host is not reachable.
            return .notReachable
        }
        else if flags.contains(.isWWAN) == true {
            // WWAN connections are OK if the calling application is using the CFNetwork APIs.
            return .reachableViaWWAN
        }
        else if flags.contains(.connectionRequired) == false {
            // If the target host is reachable and no connection is required then we'll assume that you're on Wi-Fi...
            return .reachableViaWiFi
        }
        else if (flags.contains(.connectionOnDemand) == true || flags.contains(.connectionOnTraffic) == true) && flags.contains(.interventionRequired) == false {
            // The connection is on-demand (or on-traffic) if the calling application is using the CFSocketStream or higher APIs and no [user] intervention is needed
            return .reachableViaWiFi
        }
        else {
            return .notReachable
        }
    }
}

Em qualquer método, use a condição abaixo

if currentReachabilityStatus == .notReachable {
    // Network Unavailable
 } else {
    // Network Available
 }

aqui minha solução para o swift 2.3 com a lib ( Reachability.swift )

Entre no seu Podfilee adicione:

pod 'ReachabilitySwift', '~> 2.4' // swift 2.3

Depois, no seu terminal:

pod install

Em seguida, crie um novo arquivo ReachabilityManagere adicione o código abaixo:

import Foundation
import ReachabilitySwift

enum ReachabilityManagerType {
    case Wifi
    case Cellular
    case None
}

class ReachabilityManager {
    static let sharedInstance = ReachabilityManager()

    private var reachability: Reachability!
    private var reachabilityManagerType: ReachabilityManagerType = .None


    private init() {
        do {
            self.reachability = try Reachability.reachabilityForInternetConnection()
        } catch {
            print("Unable to create Reachability")
            return
        }

        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ReachabilityManager.reachabilityChanged(_:)),name: ReachabilityChangedNotification,object: self.reachability)
        do{
            try self.reachability.startNotifier()
        }catch{
            print("could not start reachability notifier")
        }
    }

    @objc private func reachabilityChanged(note: NSNotification) {

        let reachability = note.object as! Reachability

        if reachability.isReachable() {
            if reachability.isReachableViaWiFi() {
                self.reachabilityManagerType = .Wifi
            } else {
                self.reachabilityManagerType = .Cellular
            }
        } else {
            self.reachabilityManagerType = .None
        }
    }
}

extension ReachabilityManager {

    func isConnectedToNetwork() -> Bool {
        return reachabilityManagerType != .None
    }

}

Como usá-lo:

entre no seu AppDelegate.swifte adicione o código abaixo:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
     ReachabilityManager.sharedInstance
}

Então, quando você quiser verificar se o dispositivo está conectado à Internet, faça:

if ReachabilityManager.sharedInstance.isConnectedToNetwork() {
   // Connected
} else {
  // Not connected
}

Embora possa não determinar diretamente se o telefone está conectado a uma rede, a solução mais simples (mais limpa?) Seria 'executar ping' no Google ou em outro servidor (o que não é possível, a menos que o telefone esteja conectado a uma rede) ):

private var urlSession:URLSession = {
    var newConfiguration:URLSessionConfiguration = .default
    newConfiguration.waitsForConnectivity = false
    newConfiguration.allowsCellularAccess = true
    return URLSession(configuration: newConfiguration)
}()

public func canReachGoogle() -> Bool
{
    let url = URL(string: "https://8.8.8.8")
    let semaphore = DispatchSemaphore(value: 0)
    var success = false
    let task = urlSession.dataTask(with: url!)
    { data, response, error in
        if error != nil
        {
            success = false
        }
        else
        {
            success = true
        }
        semaphore.signal()
    }

    task.resume()
    semaphore.wait()

    return success
}

Se você está preocupado com o fato de o servidor estar inativo ou bloquear seu IP, você sempre pode executar ping em vários servidores de maneira semelhante e retornar se algum deles é acessível. Ou peça a alguém que configure um servidor dedicado apenas para esse fim.