ios 监听网络状态

import Foundation
import SystemConfiguration

class NetworkMonitor {
    private let reachability = SCNetworkReachabilityCreateWithName(nil, "www.google.com")

    func startMonitoring() {
        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = Unmanaged.passRetained(self).toOpaque()

        SCNetworkReachabilitySetCallback(reachability, { (_, flags, info) in
            let reachability = Unmanaged<NetworkMonitor>.fromOpaque(info!).takeUnretainedValue()
            reachability.notifyListener(flags)
        }, &context)

        SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetCurrent(), CFRunLoopMode.defaultMode.rawValue)
    }

    private var listener: ((SCNetworkReachabilityFlags) -> Void)?

    func notifyListener(_ flags: SCNetworkReachabilityFlags) {
        let isReachable = flags.contains(.reachable)
        let needsConnection = flags.contains(.connectionRequired)
        let isNetworkAvailable = isReachable && !needsConnection

        listener?(flags)
    }

    func stopMonitoring() {
        SCNetworkReachabilityUnscheduleFromRunLoop(reachability, CFRunLoopGetCurrent(), CFRunLoopMode.defaultMode.rawValue)
    }

    deinit {
        stopMonitoring()
    }
}

// Usage
let monitor = NetworkMonitor()
monitor.listener = { flags in
    if flags.contains(.reachable) {
        print("Network is reachable")
    } else {
        print("Network is not reachable")
    }
}
monitor.startMonitoring()