turbo-modules

name

turbo-modules

description

TurboModule spec, JSI binding injection, and platform native module entry points. Use when adding a new native method to NativeAudioAPIModule.ts, wiring a new top-level HostObject through AudioAPIModuleInstaller, debugging "native module not found" or "undefined is not a function" for a global, or understanding the install() bootstrap flow on iOS and Android. Trigger phrases: "native module not found", "install()", "NativeAudioAPIModule", "injectJSIBindings", "AudioAPIModuleInstaller", "JSI global", "TurboModule spec", "module bootstrap", "undefined is not a function".

Skill: TurboModules & JSI Installation

When to Use TurboModule vs HostObjects

Rule: if it needs AVAudioSession, AudioManager, MediaSession, or OS permissions → TurboModule. If it's audio processing → HostObject installed by AudioAPIModuleInstaller.

Use TurboModule method	Use HostObject property/method
Platform system APIs (audio session, permissions, notifications, device routing)	All audio graph operations (create/connect/disconnect nodes, AudioParam, scheduling)
One-time initialization (install)	Real-time playback control
Features that need native UI thread or system callbacks	Features that only need the JSI runtime
Android-only or iOS-only behavior	Cross-platform C++ engine behavior

Most audio nodes do not need a TurboModule method — they are exposed entirely through JSI HostObjects injected by injectJSIBindings.

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Reference

• RN TurboModules (new arch): https://reactnative.dev/docs/the-new-architecture/pure-cxx-modules
• RN JSI: https://reactnative.dev/docs/the-new-architecture/architecture-glossary#javascript-interface-jsi
• fbjni (Android JNI bridge): https://github.com/facebookincubator/fbjni

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The Big Picture

Most audio functionality is exposed not through TurboModule method calls but through JSI HostObjects placed directly on the JS global object. The TurboModule's job is narrow:

1. Be available early via the standard RN module system
2. Provide install() — one synchronous call that injects HostObject factories onto globalThis
3. Expose platform-specific system APIs (audio session, permissions, notifications, devices) that cannot be done through pure JSI

flowchart TD
  A["JS: NativeAudioAPIModule.install()"]

  subgraph ios["iOS — AudioAPIModule.mm"]
    B["init AudioSessionManager · AudioEngine\nget jsi::Runtime* · CallInvoker"]
  end

  subgraph android["Android — AudioAPIModule.kt + .cpp"]
    C["MediaSessionManager.initialize()\nJNI: injectJSIBindings()"]
  end

  D["AudioAPIModuleInstaller::injectJSIBindings\n(runtime, callInvoker, eventRegistry, uiRuntime?)"]

  subgraph globals["globalThis — set by injectJSIBindings"]
    G["createAudioContext\ncreateOfflineAudioContext\ncreateAudioRecorder\ncreateAudioBuffer\ncreateAudioDecoder\ncreateAudioStretcher\nAudioEventEmitter HostObject"]
  end

  A --> ios
  A --> android
  ios --> D
  android --> D
  D --> globals

After install() returns, TypeScript code can call globalThis.createAudioContext(sampleRate) and get back a HostObject — no serialization, no bridge round-trip.

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TurboModule Spec (src/specs/NativeAudioAPIModule.ts)

Defines the TypeScript interface for the native module. Codegen (React Native's codegen) generates the native binding glue from this file.

interface Spec extends TurboModule {
  install(): boolean;                           // synchronous — MUST run first
  getDevicePreferredSampleRate(): number;       // synchronous
  setAudioSessionActivity(enabled: boolean): Promise<boolean>;
  setAudioSessionOptions(...): void;
  observeAudioInterruptions(focusType, enabled): void;
  requestRecordingPermissions(): Promise<PermissionStatus>;
  // ... audio devices, notifications ...
}

const NativeAudioAPIModule = TurboModuleRegistry.get<Spec>('AudioAPIModule')!;

install() is synchronous (RCT_EXPORT_BLOCKING_SYNCHRONOUS_METHOD on iOS, override fun install(): Boolean on Android). It must complete before the app tries to use any audio API. It is called once during module bootstrap in src/AudioAPIModule/index.ts.

Web mock (src/specs/NativeAudioAPIModule.web.ts): on the web platform, the whole spec is mocked with no-ops and resolved promises (e.g. permissions always return 'Granted'). This file replaces the native spec at bundle time for web builds.

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AudioAPIModuleInstaller (common/cpp/audioapi/AudioAPIModuleInstaller.h)

The single C++ class that owns JSI injection. It is #include-d by both iOS (.mm) and Android (.cpp) native modules, keeping the injection logic platform-agnostic.

class AudioAPIModuleInstaller {
 public:
  static void injectJSIBindings(
      jsi::Runtime *jsiRuntime,
      const std::shared_ptr<react::CallInvoker> &jsCallInvoker,
      const std::shared_ptr<AudioEventHandlerRegistry> &audioEventHandlerRegistry,
      std::shared_ptr<worklets::WorkletRuntime> uiRuntime = nullptr);
};

Each get*Function() private method creates a jsi::Function via jsi::Function::createFromHostFunction(). The lambda captures the dependencies it needs (jsCallInvoker, audioEventHandlerRegistry, uiRuntime) by value (shared_ptr).

Worklets guard: functions that need the worklets runtime (AudioContext, OfflineAudioContext) have an #if RN_AUDIO_API_ENABLE_WORKLETS branch:

#if RN_AUDIO_API_ENABLE_WORKLETS
  auto runtimeRegistry = RuntimeRegistry{.uiRuntime = uiRuntime};
  if (count > 1 && args[1].isObject()) {
    runtimeRegistry.audioRuntime = worklets::extractWorkletRuntime(runtime, args[1]);
  }
#else
  auto runtimeRegistry = RuntimeRegistry{};
#endif

Adding a new top-level global: add a static jsi::Function getCreateXxxFunction(...) private method and a setProperty("createXxx", ...) call in injectJSIBindings. This is only needed for objects that JS creates directly (not objects created as properties of another HostObject).

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iOS Native Module (AudioAPIModule.mm)

Uses ObjC++ with RCT_EXPORT_MODULE and RCT_EXPORT_BLOCKING_SYNCHRONOUS_METHOD.

Key steps in install:

1. Allocate platform managers (AudioSessionManager, AudioEngine, SystemNotificationManager, NotificationRegistry)
2. Get jsi::Runtime * from the bridge: reinterpret_cast<facebook::jsi::Runtime *>(self.bridge.runtime)
3. Get CallInvoker — different paths for old Bridge vs New Architecture:

   #if defined(RCT_NEW_ARCH_ENABLED)
     auto jsCallInvoker = _callInvoker.callInvoker;
   #else
     auto jsCallInvoker = self.bridge.jsCallInvoker;
   #endif
   

4. Create AudioEventHandlerRegistry (owns JS callbacks, needs runtime + callInvoker)
5. Call AudioAPIModuleInstaller::injectJSIBindings(...)

New Architecture support (getTurboModule):

#ifdef RCT_NEW_ARCH_ENABLED
- (std::shared_ptr<facebook::react::TurboModule>)getTurboModule:
    (const facebook::react::ObjCTurboModule::InitParams &)params
{
  return std::make_shared<facebook::react::NativeAudioAPIModuleSpecJSI>(params);
}
#endif

This connects the ObjC implementation to the codegen-generated C++ TurboModule spec.

methodQueue: the module runs on a dedicated serial queue (com.swmansion.audioapi.MainModuleQueue), not the main thread.

invokeHandlerWithEventName:eventBody:: called from Objective-C system callbacks (audio session interruption, volume change, etc.) to fire events back into JS. It converts NSDictionary to std::unordered_map<std::string, EventValue> and calls audioEventHandlerRegistry_->invokeHandlerWithEventBody(...).

---

Android Native Module (AudioAPIModule.kt + AudioAPIModule.cpp)

Android uses fbjni HybridObject — a pattern where a Kotlin class holds a C++ peer via HybridData. The Kotlin class handles the Java/Kotlin TurboModule protocol; the C++ peer owns the JSI runtime pointer and call invoker.

Initialization flow

AudioAPIModule.kt (init block)
  ├── System.loadLibrary("react-native-audio-api")        // load .so
  ├── get CallInvokerHolderImpl from reactContext
  ├── get WorkletsModule if worklets enabled
  └── mHybridData = initHybrid(workletsModule, jsContext, callInvokerHolder)
            │
            ▼
      AudioAPIModule.cpp::initHybrid (JNI)
        ├── unwrap jsCallInvoker from holder
        ├── reinterpret_cast<jsi::Runtime *>(jsContext)
        ├── [if worklets] get WorkletsModuleProxy
        └── makeCxxInstance(...)   → creates C++ AudioAPIModule peer
                └── stores: jsiRuntime_, jsCallInvoker_, audioEventHandlerRegistry_

AudioAPIModule.kt::install()
  ├── MediaSessionManager.initialize(...)
  ├── NativeFileInfo.initialize(...)
  └── injectJSIBindings()   // external fun → JNI call
            │
            ▼
      AudioAPIModule.cpp::injectJSIBindings()
        └── AudioAPIModuleInstaller::injectJSIBindings(...)

external fun: Kotlin keyword for JNI-implemented methods. These are registered in AudioAPIModule.cpp::registerNatives():

void AudioAPIModule::registerNatives() {
  registerHybrid({
    makeNativeMethod("initHybrid",          AudioAPIModule::initHybrid),
    makeNativeMethod("injectJSIBindings",   AudioAPIModule::injectJSIBindings),
    makeNativeMethod("invokeHandlerWithEventNameAndEventBody", ...),
  });
}

registerNatives() is called from android/src/main/cpp/audioapi/android/OnLoad.cpp at .so load time.

invokeHandlerWithEventNameAndEventBody: called from Kotlin (MediaSessionManager callbacks) to fire events into JS. Takes a Java Map<String, Object> and converts to std::unordered_map<std::string, EventValue>.

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Two-Architecture Paths Summary

	Old Bridge	New Architecture (TurboModules/Fabric)
iOS CallInvoker source	self.bridge.jsCallInvoker	_callInvoker.callInvoker
iOS runtime source	self.bridge.runtime (cast)	same
iOS codegen	RCT_EXPORT_MODULE only	+ getTurboModule: implemented
Android CallInvoker	reactContext.jsCallInvokerHolder	same
Android codegen	NativeAudioAPIModuleSpec base class	same (generated)

The JSI injection itself (AudioAPIModuleInstaller) is identical for both architectures — it only needs the jsi::Runtime * and CallInvoker, which are obtained differently but behave the same.

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Maintenance: see maintenance.md.