Is there any way to cancel messages sent by the sendMessage(_:replyHandler:errorHandler:) method of WCSession?
From the documentation:
Messages are queued serially and delivered in the order in which you sent them.
No. That type of transfer is not cancellable, as
the OS would have immediately sent any sendMessage data to a reachable counterpart
Use the [sendMessage] method to transfer data to a reachable counterpart. These methods are intended for immediate communication between your iOS app and WatchKit extension.
Data sent using the [sendMessage], and
transferCurrentComplicationUserInfo:methods has a higher priority and is transmitted right away.
the OS provides no mechanism to specifically cancel a message
The only WCSession objects that have a cancel method are WCSessionUserInfoTransfer, and WCSessionFileTransfer, since lower-priority transferUserInfo or transferFile data is not sent immediately, but at an optimum time determined by the OS.