I've a problem, with my app.. I try to follow some guide like Passing data to Apple Watch app , but I'm not sure it will fit for my case. I've some label with text on my iOS app, then I want to show this text on my watchOS app label, and I don't know which is the best way to pass this text and keep it synchronized with the iOS app.. Thanks a lot for your help!
Since watchOS2, you don't have any built in function for communicating between the iOS and watchOS app than the WatchConnectivity framework.
From the information provided in your question, the updateApplicationContext(_:) function seems to be the best solution for your problem. You can send a dictionary of data with this function and the system tries to make sure that the data is received by the time your app is displayed to the user. If the function is called several times before the app would be visible to the user (run in the foreground), the system overwrites the previous data, so the Watch app only receives the most recent data to display.