not able to hook the event for the state of article change to publish for the iOS app push notifications

i have developed an iOS app with wordpress as backend and i have written the server side code for the same.

Now, i need to run my code when ever a post is published. Also i need to create a table to store the ids of the iOS devices so that when ever an new post is published, the notification is sent to all the registered devices automatically.

I am not able to figure out how to do so .

Any suggestion would be grteat.

Thanks in advance!