In fact, watchOS apps are associated with an iOS app.
In both versions, each watchOS application has two goals: WatchKit App - contains a storyboard, icons, etc. and a WatchKit extension containing code.
In watchOS 1 (old WatchKit) + iOS 8, the WatchKit application is installed on the Apple Watch, and both the WatchKit Extension and iOS applications are installed on the user's iPhone.
In another way, in the watchOS 2 + iOS 9 combination, both the WatchKit App and WatchKit Extension are installed on the Apple Watch user, and the iOS application is the only code and view installed on the iPhone.
Launching an iOS application requires only one goal, so it can work without an Apple Watch (starting with the first iPhone OS).
But to run watchOS applications, the WatchKit and WatchKit Extension applications are required. In watchOS 1 (old WatchKit), because one is on the iPhone and the other is on the Apple Watch, so applications need a connection between them with Bluetooth, so you need to carry your iPhone nearby. In watchOS 2, both are on the Apple Watch, so you do not need to connect to the iPhone and have an iPhone nearby to run applications. You can associate them with the WatchConnectivity framework included in the watchOS 2 SDK (in Xcode 7).
So in watchOS 2 applications can work autonomously, but they are not autonomous at all. They are installed on the Apple Watch when installed on the iPhone, and they can connect to each other. When you create a new watchOS application, you must include it in the iPhone application when sending it to iTunes Connect.
NOTE. This makes watchOS applications faster and more reliable.
Seyyed Parsa Neshaei
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