Mobile development is mainly separated into two models, native and cross platform. Native mobile applications are generally built using Kotlin/Java on Android and Swift/Objective-C on iOS. And for cross platform development, there are Flutter and React Native as the leaders of this model. Spruce's primary development pattern has been to architect Credible as a Flutter application that integrates DIDKit as a C library through the Dart FFI. When a client wants to integrate Credible into their own application, the easiest way to do so is if the client’s relying application is itself also built in Flutter.
It is also possible, however, to decouple a Credible SDK from the Credible application and distribute it for use in native-only development. A developer that already has a native solution and wants to integrate Credible's lower-level libraries would be averse to taking on a dependency to the entire Flutter SDK just for what might otherwise be a much smaller native library used only to handle the Verifiable-Credential specific cryptography and other mechanics.
For this development context, our native SDK is made by re-implementing sections of the Credible codebase in Swift for native iOS development and Kotlin for native Android development. As this development tooling is still under development, these have to be built from source for now, and instructions for doing so can be found in the repos (see below). At a later stage of maturity, we expect to distribute binaries through the respective package managers.
Swift developers can find instructions for building DIDKit as a Swift dependency in the /lib/ios folder of the didkit repo.
Kotlin developers can find a DIDKit package for maven in the packages section of the didkit repo.
For reference documentation on how to interact with a C library from Kotlin FFI, see this section of the official Kotlin documentation. For the equivalent in Swift, see this section of the official Swift documentation.