Let say the iphone has a text field or any internal data, upon the data change, I want to push it automatically to the Apple Watch. I know I can use the share data. But that seems to require user to initiate the call (e.g. pressing a button) on the Watch. Is there a listener on the Apple Watch that I can use if there is a change in the share data? or there is way for iPhone to automatcially push data to the Watch, and the Watch just receive it and display it? or any other way?
How can Apple watch listen to data change in iPhone
The way to do this is described in the WWDC session on Watch Connectivity. For this kind of immediate communication, you can use WCSession's sendMessage to send data to the app running on the watch. To get the data upon change to the text field, you'll need to implement the delegate method that responds to changes in the text field, then send that data to the watch, and respond to the appropriate delegate calls on the watch when it receives those messages.