Question

If I click a button in “Awesome App”, is there any way to send a short text message to nearby users who also have “Awesome App” installed? This could be via bluetooth, wifi, 3g or any other way you smart people can suggest.

Answer 1

You can register the app for geo updates, submit the location to your server and when the user sends a message this message will be send to your server, the location is checked and all nearby users receive a push notification with this message.

Also make sure that they can fetch the message from the server as well, as push notification delivery isn’t guaranteed.

To update the location of the app you call

self.locationManager = [[CLLocationManager alloc] init];
[self.locationManager startMonitoringSignificantLocationChanges];

If you don’t need updates anymore, make sure to call

[self.locationManager stopMonitoringSignificantLocationChanges];

Also make sure to set the location value in the info.plist‘s UIBackgroundModes key.

This will give you locations changes while your app is in the background and, according to the documentation, will even restart your app if it has been terminated.