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Using Nitro in a library

Nitro can be used as a simple C++ library in your React Native library, which is very lightweight and simple.

1. Create a Nitro Module​

First, you need to create a Nitro Module - either by just using the Nitro Modules template, or by just adding react-native-nitro-modules to your existing React Native library.

2. Create Hybrid Objects​

To actually use Nitro, you need to create Hybrid Objects - either by using Nitro's code-generator CLI “Nitrogen”, or by just manually extending the HybridObject base class in C++.

3. Register Hybrid Objects​

Each Hybrid Object you want to initialize from JS has to be registered in Nitro - either by autolinking them with Nitrogen (see Configuration (Autolinking)), or by manually registering the constructors in the HybridObjectRegistry.

4. Use your Hybrid Objects in JS​

Lastly, you can initialize and use the registered Hybrid Objects from JS. This is what this will ultimately look like:

interface Math extends HybridObject {
  add(a: number, b: number): number
}

const math = NitroModules.createHybridObject<Math>("Math")
const value = math.add(5, 7) // --> 12

5. Run it​

To test the library you just created, you now need to set up an example app for it. There's multiple different ways to set up a react-native app nowadays, either via Expo, RN CLI, or bare brownfield iOS/Android apps.

For example, to create a new Expo app, run create-expo-app:

npx create-expo-app@latest

Then add the Nitro Module you created in step 1 as a local library (aka linking it), and run it.