Receiving a call

Now that the calling interface is built, you can now add the code needed receive a call. The NXMClientDelegate has a function that is called when there is an incoming call. Add an implementation for it in the NXMClientDelegate extension in the ViewController.swift file.

extension ViewController: NXMClientDelegate {

    func client(_ client: NXMClient, didReceive call: NXMCall) {
        nc.post(name: .call, object: call)

extension Notification.Name {
    static var call: Notification.Name {
        return .init(rawValue: "NXMClient.incomingCall")

The CallViewController class will be in the foreground and the class handling the call, so the call is passed along using a NSNotification post. For CallViewController to receive this notification it needs to observe it. In the CallViewController add.

class CallViewController: UIViewController {

    override func viewDidLoad() {

        nc.addObserver(self, selector: #selector(didReceiveCall), name: .call, object: nil)

        hangUpButton.addTarget(self, action: #selector(endCall), for: .touchUpInside)


    @objc private func didReceiveCall(_ notification: Notification) {
        guard let call = notification.object as? NXMCall else { return }
        DispatchQueue.main.async { [weak self] in
            self?.displayIncomingCallAlert(call: call)

    private func displayIncomingCallAlert(call: NXMCall) {
        var from = "Unknown"
        if let otherParty = call.otherCallMembers.firstObject as? NXMCallMember {
            from = otherParty.user.name

        let alert = UIAlertController(title: "Incoming call from", message: from, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "Answer", style: .default, handler: { _ in
            call.answer { error in
                if error != nil {
                self.setStatusLabelText("On a call with \(from)")
                self.call = call

        alert.addAction(UIAlertAction(title: "Reject", style: .destructive, handler: { _ in

        self.present(alert, animated: true, completion: nil)

    @objc private func endCall() {
        self.setStatusLabelText("Ready to receive call...")

When a notification is received didReceiveCall is called which in turn calls displayIncomingCallAlert to present the user with the option of accepting or rejecting the call. If the user accepts the UI is updated to show who the user is on a call with and the hangUpButton becomes visible. If the hangUpButton is tapped endCall is called which hangs up the call and updates the UI.

The call delegate

Similar to NXMClient, NXMCall also has a delegate to handle changes to the call. To the end of the CallViewController.swift file add the conformance to the NXMCallDelegate.

extension CallViewController: NXMCallDelegate {
    func call(_ call: NXMCall, didUpdate callMember: NXMCallMember, with status: NXMCallMemberStatus) {
        switch status {
        case .answered:
            guard callMember.user.name != self.user.name else { return }
            setStatusLabelText("On a call with \(callMember.user.name)")
        case .completed:
            setStatusLabelText("Call ended")
            self.call = nil

    func call(_ call: NXMCall, didReceive error: Error) {

    func call(_ call: NXMCall, didUpdate callMember: NXMCallMember, isMuted muted: Bool) {}

In the next step you will add the code needed to make a call.