Observe WiFi / 3G changes

Question

Is it possible to observe when the user switch between WiFi and cellular data (3G/4G)?

Maybe something in Reachability, but I don't know what.

Answer 1

The easiest way I think is import CoreTelephony and observe CTRadioAccessTechnologyDidChangeNotification and then switch over that like this:

let networkInfo = CTTelephonyNetworkInfo()
let radio = networkInfo.currentRadioAccessTechnology

guard let currentRadio = radio else {
   print("No radio info available")
   return
}

switch currentRadio {
   case CTRadioAccessTechnologyLTE,
        CTRadioAccessTechnologyHSDPA: //3.5G "T-Mobile 4G"
       print("This is 4G / LTE")
   case CTRadioAccessTechnologyeHRPD, //3.5G "Verizon 3G"
        CTRadioAccessTechnologyHSUPA,
        CTRadioAccessTechnologyWCDMA,
        CTRadioAccessTechnologyCDMAEVDORev0,
        CTRadioAccessTechnologyCDMAEVDORevA,
        CTRadioAccessTechnologyCDMAEVDORevB:
      print("This is 3G")
   case CTRadioAccessTechnologyGPRS,
        CTRadioAccessTechnologyCDMA1x
        CTRadioAccessTechnologyEdge:
      print("This is 2G")
   default:
      print("Unknown cellular network type")
   }

If you listen for that notification while also using standard Reachability, you can use this switch to get cell network type. You will need currentReachabilityStatus to independently check for a WiFi connection. As far as I am aware, in Swift you need to set up a bridging header to use Apple's Reachability class but there are Swift implementations available as well on github.