The watchOS SDK provides all the types and classes made available by Apple for creating applications for Apple Watch (running watchOS 2.0 or later).

Each Cocoa SDK is spread over several frameworks and core include files. The core C APIs are located in rtl.fx, which is a package containing pretty much everything defined in /usr/include. The base framework of core Cocoa classes is called "Foundation" (shared with macOS), and contains, among many other things, NSObject, the base type for all Cocoa classes.

More frameworks are shared across sub-platforms, while each sub-platform also provides its own unique frameworks.

Please refer to the Introduction to the Frameworks topic for more information on how the frameworks fit together, and how they differ between the (currently) four separate Cocoa platforms.

For all the SDK frameworks, the Namespace used matches the framework name.

watchOS is loosely derived from iOS, but has a severely reduced feature set, and a different model for building user interfaces – the WatckKit and ClockKit frameworks, respectively. It does not provide UIKit-level UI access (although it is build upon UIKit).

See Also

macOSiOSwatchOStvOSMac Catatyst