How to use x-callback-url?

Question

I want to open an app and return from it with some return values like success or fail. How to do it?

From the documentation

[scheme]://[host]/[action]?[x-callback parameters]&[action parameters]

Question 1:

What should I place in [action parameters]? Is it compulsory?

Sending App A

- (IBAction)openReceivingAppBButtonPressed:(id)sender {

    NSString *xcallBack = @"x-callback-url/payment?&amount=1.00";
    NSString *URLEncodedText = [xcallBack stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *ourURL = [NSURL URLWithString:[@"receivingAppB://" stringByAppendingString:URLEncodedText]];
    if([[UIApplication sharedApplication] canOpenURL:ourURL]){
        [[UIApplication sharedApplication] openURL:ourURL];
    }
}

Receiving App B

- (BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url{

    [self returnToSendingAppAWithResponse];

    return true;
}
-(void)returnToSendingAppAWithResponse{
    NSString *xcallBackSuccess = @"success";

    NSString *URLEncodedText = [xcallBackSuccess stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *ourURL = [NSURL URLWithString:[@"sendingAppA://" stringByAppendingString:URLEncodedText]];
    if([[UIApplication sharedApplication] canOpenURL:ourURL]){
        [[UIApplication sharedApplication] openURL:ourURL];
    }
}

Question 2:

In the receiving app, is it correct to call another openURL call to the Sending App A to return the success message?

I'm able to achieve what I want. But just doubt whether this is the correct way of using x-callback-url. x-callback-url doesn't seem to be useful to me.

Answer 1

Seems like the above mentioned method is the correct way of doing it.

x-callback is just a "protocol" to format the NSURL to ease the data processing at the receiver end and also allowed the source app to receive the correct callback function. (e.g. which action name should be call)