Entry Point
Nitro is built on top of JSI - while the primary target is React Native, Nitro even works on any other target that provides JSI.
React Native's Entry Point
In React Native apps, Nitro makes use of the autolinking functionality provided by RN CLI.
react-native-nitro-modules requires React Native 0.78 or higher with the New Architecture. Importing the package resolves its TurboModule, which synchronously installs Nitro through React Native's JSI bindings hook: installJSIBindingsWithRuntime:callInvoker: on iOS and getBindingsInstaller() on Android.
React Native passes the JavaScript runtime and its CallInvoker to the installation callback. Nitro wraps the invoker in a Dispatcher and installs NitroModulesProxy before the import completes.
Manually registering Nitro
If you are not within a typical React Native environment (e.g. a brownfield app, an out-of-tree platform, or simply a pure JSI environment), you can also use Nitro Modules by just installing Nitro manually.
After creating your jsi::Runtime and an instance of Dispatcher, simply call margelo::nitro::install():
#include <jsi/jsi.h>
#include <NitroModules/InstallNitro.hpp>
#include <NitroModules/Dispatcher.hpp>
jsi::Runtime& runtime = ...
std::shared_ptr<Dispatcher> dispatcher = ...
margelo::nitro::install(runtime, dispatcher);
Your Dispatcher implementation must properly implement runAsync and runSync to schedule calls on a Thread that can safely access the jsi::Runtime.
If your Runtime can be accessed from any Thread, you can also skip Thread-hops here and just call the functions directly in your Dispatcher.
No Dispatcher
Nitro can also be installed without a Dispatcher:
#include <jsi/jsi.h>
#include <NitroModules/InstallNitro.hpp>
jsi::Runtime& runtime = ...
margelo::nitro::install(runtime);
In this case, all synchronous methods and properties remain in-tact, but any asynchronous hybrid methods (Promise) or callbacks will throw an error that Nitro does not have a Dispatcher to get back to the JS Thread.