我使用NSTimer和Alamofire制作了自己的解决方案:

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()
    }
}

NSTimer被用作超时，并且由于使用Alamofire超时的不可靠结果而被使用。请求应该发送到您认为可靠的URL，例如您自己的服务器或托管您所依赖的服务的服务器。

当计时器过期时，请求将被取消，并使用完成处理程序返回结果。

用法:

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

我改进了莱科斯的例子。我添加了一些额外的控件来解决双重触发问题，还添加了通知支持来侦听状态更改。

我为防止双重触发问题而添加的控件还显示了设备主要使用哪个连接源来访问互联网。

例如，即使设备同时连接到蜂窝网络和Wi-Fi，“状态”返回为“connectedViaWiFi”，以指示当前的互联网访问是通过Wi-Fi。

import Foundation
import Network

class Reachability {

    enum StatusFlag {
        case unknow
        case noConnection
        case connectedViaWiFi
        case connectedViaCellular
    }

    static let connectionStatusHasChangedNotification = NSNotification.Name("Reachability.connectionStatusHasChangedNotification")
    static let shared = Reachability()

    private var monitorForWifi: NWPathMonitor?
    private var monitorForCellular: NWPathMonitor?
    private var wifiStatus: NWPath.Status = .requiresConnection
    private var cellularStatus: NWPath.Status = .requiresConnection
    private var ignoreInitialWiFiStatusUpdate: Bool = true
    private var ignoreInitialCelluluarStatusUpdate: Bool = true
    private var isReachableOnCellular: Bool { cellularStatus == .satisfied }
    private var isReachableOnWiFi: Bool { wifiStatus == .satisfied }
    var status: StatusFlag = .unknow {
        didSet {
            guard status != oldValue else { return }
            DispatchQueue.main.async { [weak self] in
                NotificationCenter.default.post(name: Self.connectionStatusHasChangedNotification,
                                                object: self?.status)
            }
        }
    }

    func startMonitoring() {
        monitorForWifi = NWPathMonitor(requiredInterfaceType: .wifi)
        monitorForWifi?.pathUpdateHandler = { [weak self] path in
            self?.wifiStatus = path.status
            self?.ignoreInitialWiFiStatusUpdate = false
            self?.updateStatus()
        }
        monitorForCellular = NWPathMonitor(requiredInterfaceType: .cellular)
        monitorForCellular?.pathUpdateHandler = { [weak self] path in
            self?.cellularStatus = path.status
            self?.ignoreInitialCelluluarStatusUpdate = false
            self?.updateStatus()
        }
        let queue = DispatchQueue.global(qos: .background)
        monitorForCellular?.start(queue: queue)
        monitorForWifi?.start(queue: queue)
    }

    func stopMonitoring() {
        monitorForWifi?.cancel()
        monitorForWifi = nil
        monitorForCellular?.cancel()
        monitorForCellular = nil
        wifiStatus = .requiresConnection
        cellularStatus = .requiresConnection
        status = .unknow
        ignoreInitialWiFiStatusUpdate = true
        ignoreInitialCelluluarStatusUpdate = true
    }

    private func updateStatus() {
        if ignoreInitialWiFiStatusUpdate || ignoreInitialCelluluarStatusUpdate {
            return
        }
        if !(isReachableOnCellular && isReachableOnWiFi) {
            if isReachableOnCellular && !isReachableOnWiFi {
                status = .connectedViaCellular
            } else if isReachableOnWiFi && !isReachableOnCellular {
                status = .connectedViaWiFi
            } else {
                status = .noConnection
            }
        } else {
            status = .connectedViaWiFi
        }
    }

    static func isConnectedToNetwork() -> Bool {
        return shared.isReachableOnCellular || shared.isReachableOnWiFi
    }
}

示例使用

    override func viewDidLoad() {
        super.viewDidLoad()
        NotificationCenter.default.addObserver(self, selector: #selector(reachabilityChanged(_:)), name: Reachability.connectionStatusHasChangedNotification, object: nil)
        Reachability.shared.startMonitoring()
    }

    @objc func reachabilityChanged(_ sender: Notification) {
        guard let statusFlag = sender.object as? Reachability.StatusFlag else { return }
        print("TEST -> statusFlag: \(statusFlag)")
    }

Xcode 14.0, Swift 5.7

要检查互联网连接，请使用苹果的本地网络框架。它有NWPathMonitor类观察者，你可以实现它来监视和响应网络变化。

import Network

class ViewController: UIViewController {       
    @IBOutlet var label: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.networkMonitoring()
    }
    
    fileprivate func networkMonitoring() {
        let monitor = NWPathMonitor()
        let queue = DispatchQueue(label: "monitoring")
        monitor.start(queue: queue)
        
        monitor.pathUpdateHandler = { path in
            DispatchQueue.main.async {
                switch path.status {
                    case .satisfied:
                        self.label.text = "Intenet connected"
                        self.view.backgroundColor = .systemGreen
                    case .unsatisfied:
                        self.label.text = "No Intenet"
                        self.view.backgroundColor = .systemRed
                    case .requiresConnection:
                        self.label.text = "May be activated"
                        self.view.backgroundColor = .systemBlue
                    @unknown default:  fatalError()
                }
            }
        }
    }
}

为了解决评论中提到的4G问题，我使用@AshleyMills的可达性实现作为参考，重写了Swift 3.1的可达性:

更新:Xcode 10.1•Swift 4或更高版本

Reachability.swift文件

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)
    }
}

使用

在你的AppDelegate.swift didFinishLaunchingWithOptions方法中初始化它，并处理任何可能发生的错误:

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
    }
}

和一个视图控制器示例:

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()
    }
}

示例项目

如果有人已经在使用Alamofire，那么-

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

用法:

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

我已经检查了实现阿什利米尔的可达性类没有可可荚/依赖管理器。其思想是使项目中的可达性依赖项免费。

Xcode 7.2 - Swift 2.1

1) https://github.com/ashleymills/Reachability.swift。下载将Reachability类添加到项目中。

注:添加时，请确保勾选“如需复制项目”。

2)创建一个AppManager.swift类。这个类将迎合公共模型类，其中公共方法和数据将被添加，可以在任何VC中使用。

//  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)创建一个委托类。我使用委托方法来通知连接状态。

//  Protocols.swift

import Foundation
@objc protocol AppManagerDelegate:NSObjectProtocol {

    func reachabilityStatusChangeHandler(reachability:Reachability)
}

4)创建UIViewController的父类(继承方法)。父类具有所有子vc都可以访问的方法。

//  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)在AppDelegate中启动实时Internet连接监控。

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

6)我已经添加了一个Swift文件名AppReference来存储常量enum值。

//  AppReference.swift

import Foundation

enum CONNECTION_NETWORK_TYPE : String {

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

}

7)在ViewController上(例如，你只想在网络可用的情况下调用API)

//  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() {
  }
}

样本可以在https://github.com/alvinreuben/Reachability-Sample上下载

升级到Swift 3.1- https://github.com/alvinvgeorge/Reachability-UpgradedToSwift3