Possible way to detect sim card detection in ios?

Question

I have a iphone app that has the capability to send messages. I want to alert user when sim card is not available in iphone. So i tried below three function to check sim car

Answer 1

Complementing to Anneq and Felipe answers:

Swift 2.3:

import CoreTelephony
func isSimAvailable()  -> Bool {
    let info = CTTelephonyNetworkInfo()
    let carr = info.subscriberCellularProvider
    guard let carrier = carr else {
        return false
    }
    guard let carrierCode = carrier.mobileNetworkCode else {
        return false
    }
    guard carrierCode != "" else {
        return false
    }
    return true
}