How to Make and Receive Voice Calls with the Nexmo Client SDK on iOS using Objective-C

In this tutorial you learn how to use Nexmo Client SDK for iOS, in order to perform an in-app (IP to IP) voice call.

You will create a simple app to make a call and receive a call.

The app will have two buttons, which log in different users: Jane or Joe. After logging in, Jane and Joe are able to place a call and perform actions such as answer, reject or hangup.

Prerequisites

Create the project

Using the Github project you cloned, in the Starter app, with XCode:

  1. Open IAVAppDefine.h file and replace the user IDs and tokens:

        #define kInAppVoiceJaneUserId @"JANE_USER_ID" //TODO: replace with a userId for Jane
        #define kInAppVoiceJaneToken @"JANE_TOKEN" //TODO: replace with a token for Jane
        #define kInAppVoiceJoeUserId @"JOE_USER_ID" //TODO: replace with a userId for Joe
        #define kInAppVoiceJoeToken @"JOE_TOKEN" //TODO: replace with a token for Joe
    
  2. Open MainViewController.m file and make sure the following lines exist:

Login

Using the Nexmo Client SDK should start with logging in to NexmoClient, using a jwt user token.

In production apps, your server would authenticate the user, and would return a correctly configured JWT to your app.

For testing and getting started purposes, you can use the Nexmo CLI to generate JWTs.

Open MainViewController.m. Explore the setup methods that were written for you on viewDidLoad.

Now locate the following line #pragma mark - Tutorial Methods and complete the setupNexmoClient method implementation:

- (void)setupNexmoClient {
    self.nexmoClient = [[NXMClient alloc] initWithToken:self.selectedUser.token];
    [self.nexmoClient setDelegate:self];
    [self.nexmoClient login];
}

Notice that self is set to be the delegate for NXMClient. Do not forget to adopt the NXMClientDelegate protocol and implement the required methods.

Add the required protocol adoption declaration to the class extension located in the MainViewController.m file:

@interface MainViewController () <NXMClientDelegate>

The NXMClientDelegate indicates if the login was successful and you can start using the SDK.

Add the following method under the #pragma mark NXMClientDelegate line.

- (void)connectionStatusChanged:(NXMConnectionStatus)status reason:(NXMConnectionStatusReason)reason {
    [self setWithConnectionStatus:status];
}

At this point you should already be able to run the app and see that you can login successfully with the SDK.

Start a Call

You can now make a simple In-App call. If you logged in as Jane, you can call Joe, and if you logged in as Joe you can call Jane.

Call Other button press is already connected to the MainViewController.

Implement the didCallOtherButtonPress: method to start a call. It will start the call, and also update the UIViews so that Jane or Joe know the call is in progress:

- (IBAction)didCallOtherButtonPress:(UIButton *)sender {
    self.isInCall = YES;
    [self.nexmoClient call:@[self.otherUser.userId] callType:NXMCallTypeInApp delegate:self completion:^(NSError * _Nullable error, NXMCall * _Nullable call) {
        if(error) {
            self.isInCall = NO;
            self.ongoingCall = nil;
            [self updateCallStatusLabelWithText:@""];
            return;
        }
        self.ongoingCall = call;
        [self setActiveViews];
    }];
}

Ensure that NSArray is initialized with otherUser.userId. You can have multiple users in a call. However, this tutorial demonstrates a 1-on-1 call.

As with NXMClient, NXMCall also receives a delegate which you supplied in the call:callType:delegate:completion: method.

Adopt the NXMCallDelegate. Your extension declaration should look like this:

@interface MainViewController () <NXMClientDelegate, NXMCallDelegate>

Copy the following implementation for the statusChanged method of the NXMCallDelegate along with the aid methods under the #pragma mark NXMCallDelegate line:

- (void)statusChanged:(NXMCallMember *)callMember {
    if([callMember.userId isEqualToString:self.selectedUser.userId]) {
        [self statusChangedForMyMember:callMember];
    } else {
        [self statusChangedForOtherMember:callMember];
    }
}

- (void)statusChangedForMyMember:(NXMCallMember *)myMember {
    [self updateCallStatusLabelWithStatus:myMember.status];

    //Handle Hangup

}

- (void)statusChangedForOtherMember:(NXMCallMember *)otherMember {

}

The statusChanged: method notifies on changes that happens to members on the call.

The statusChangedForOtherMember and statusChangedForMyMember methods are updated later when you will handle call hangup.

You can build the project now and make an outgoing call. Next you implement how to receive an incoming call.

Note that while NXMCallTypeInApp is useful for simple calls, you can also start a call with customized logic using an NCCO ), by choosing NXMCallTypeServer as the callType.

 [self.nexmoClient call:@[callees] callType:NXMCallTypeServer delegate:self completion:^(NSError * _Nullable error, NXMCall * _Nullable call){...}];

This also allows you to start a PSTN phone call, by adding a phone number to the callees array.

Receive incoming call

When Jane calls Joe, Joe should be notified, so that Joe may decide to answer or reject the call.

This is done by implementing the optional incomingCall: method which is declared in the NXMClientDelegate.

Go back to the #pragma mark NXMClientDelegate line and add the `incomingCall:' method

- (void)incomingCall:(nonnull NXMCall *)call {
    self.ongoingCall = call;
    [self displayIncomingCallAlert];
}

This method takes as a parameter an NXMCall object with which you can answer or reject the call. An alert was implemented for you, to allow the user to choose whether to answer or reject the call.

Answer a call

Under the #pragma mark IncomingCall, implement this method to answer the incoming call:

- (void)didPressAnswerIncomingCall {
    __weak MainViewController *weakSelf = self;
    [weakSelf.ongoingCall answer:self completionHandler:^(NSError * _Nullable error) {
        if(error) {
            [weakSelf displayAlertWithTitle:@"Answer Call" andMessage:@"Error answering call"];
            weakSelf.ongoingCall = nil;
            weakSelf.isInCall = NO;
            [self updateCallStatusLabelWithText:@""];
            [weakSelf setActiveViews];
            return;
        }
        self.isInCall = YES;
        [weakSelf setActiveViews];
    }];
}

answer:completionHandler accepts an object adopting the NXMCallDelegate, and a completionHandler, to indicate if an error occurred in the process. You already implemented NXMCallDelegate in a previous step.

Reject a call

Under the #pragma mark IncomingCall, implement this method to reject the incoming call:

- (void)didPressRejectIncomingCall {
    __weak MainViewController *weakSelf = self;
    [weakSelf.ongoingCall reject:^(NSError * _Nullable error) {
        if(error) {
            [weakSelf displayAlertWithTitle:@"Reject Call" andMessage:@"Error rejecting call"];
            return;
        }

        weakSelf.ongoingCall = nil;
        weakSelf.isInCall = NO;
        [self updateCallStatusLabelWithText:@""];
        [weakSelf setActiveViews];
    }];
}

reject: accepts a single completionHandler parameter to indicate if an error occurred in the process.

Hangup a call

Once Jane or Joe presses the red button, it is time to hangup the call. Implement didEndButtonPress: method and call hangup for myCallMember.

- (IBAction)didEndButtonPress:(UIButton *)sender {
    [self.ongoingCall.myCallMember hangup];
}

Updates for callMember statuses are received in statusChanged as part of the NXMCallDelegate as you have seen before.

Update the implementation for statusChangedForOtherMember and statusChangedForMyMember to handle call hangup:

- (void)statusChangedForMyMember:(NXMCallMember *)myMember {
    [self updateCallStatusLabelWithStatus:myMember.status];

    //Handle Hangup
    if(myMember.status == NXMCallMemberStatusCancelled || myMember.status == NXMCallMemberStatusCompleted) {
        self.ongoingCall = nil;
        self.isInCall = NO;
        [self updateCallStatusLabelWithText:@""];
        [self setActiveViews];
    }
}

- (void)statusChangedForOtherMember:(NXMCallMember *)otherMember {
    if(otherMember.status == NXMCallMemberStatusCancelled || otherMember.status == NXMCallMemberStatusCompleted) {
        [self.ongoingCall.myCallMember hangup];
    }
}

Handle permissions

For the call to happen, Audio Permissions are required. In the appDelegate of the sample project, you can find an implementation for the permissions request in application:didFinishLaunchingWithOptions.

To read more about the permissions required, see the setup tutorial.

Conclusion

You have implemented your first In App Voice application with the Nexmo Client SDK for iOS.

Run the app on two simulators and see that you can call, answer, reject and hangup.

If possible, test on two phones using your developer signing and provisioning facility.