In App Turbomodule

This is an example on how to create an In App Turbomodule (not an external library). To create a Turbomodule in app, we roughly have to:

1. Create the TS specs
2. Configure codegen to run on the app
3. Implement the Native Code
4. Connect The TM with JS

1. Create the TS Spec

1. Create a folder called specs where we are going to write our Codegen Specs
2. Create a file NativeLocalStorage.ts that will contain the spec for our module
3. Add the specs for the NativeLocalStorage specs

import { TurboModule, TurboModuleRegistry } from "react-native";

export interface Spec extends TurboModule {
  setString(value: string, key: string): void;
  getString(key: string): string;
}

export default TurboModuleRegistry.get<Spec>("NativeLocalStorage") as Spec | null;

Note

The spec file for Turbo Native Modules must have the prefix Native to work properly.

2. Configure Codegen

1. Open the package.json file
2. Add the codegenConfig field as it follows

   "packageManager": "yarn@3.6.4",
+   "codegenConfig": {
+      "name": "NativeLocalStorageSpec",
+      "type": "modules",
+      "jsSrcsDir": "specs",
+      "android": {
+         "javaPackageName": "com.nativelocalstorage"
+      }
+   }
}

3. Implement the Native Code

Android:

1. In the folder path android/app/src/main/java/com, create a new folder nativelocalstorage
2. Create a new file NativeLocalStorageModule.kt
3. Modify the NativeLocalStorageModule.kt with the following code:

package com.nativelocalstorage

import android.content.Context
import android.content.SharedPreferences
import com.nativelocalstorage.NativeLocalStorageSpec
import com.facebook.react.bridge.ReactApplicationContext

class NativeLocalStorageModule(reactContext: ReactApplicationContext) : NativeLocalStorageSpec(reactContext) {

  override fun getName() = NAME

  override fun setString(value: String, key: String) {
    val sharedPref = getReactApplicationContext().getSharedPreferences("my_prefs", Context.MODE_PRIVATE)
    val editor = sharedPref.edit()
    editor.putString(key, value)
    editor.apply()
  }

  override fun getString(key: String): String {
    val sharedPref = getReactApplicationContext().getSharedPreferences("my_prefs", Context.MODE_PRIVATE)
    val username = sharedPref.getString(key, "")
    return username.toString()
  }

  companion object {
    const val NAME = "NativeLocalStorage"
  }
}

4. In the same folder, create a new file NativeLocalStoragePackage.kt.
5. Modify the new file with the following code:

package com.nativelocalstorage;

import com.facebook.react.TurboReactPackage
import com.facebook.react.bridge.NativeModule
import com.facebook.react.bridge.ReactApplicationContext
import com.facebook.react.module.model.ReactModuleInfo
import com.facebook.react.module.model.ReactModuleInfoProvider

class NativeLocalStoragePackage : TurboReactPackage() {

  override fun getModule(name: String, reactContext: ReactApplicationContext): NativeModule? =
    if (name == NativeLocalStorageModule.NAME) {
      NativeLocalStorageModule(reactContext)
    } else {
      null
    }

  override fun getReactModuleInfoProvider() = ReactModuleInfoProvider {
    mapOf(
      NativeLocalStorageModule.NAME to ReactModuleInfo(
        NativeLocalStorageModule.NAME,
        NativeLocalStorageModule.NAME,
        false, // canOverrideExistingModule
        false, // needsEagerInit
        false, // isCxxModule
        true // isTurboModule
      )
    )
  }
}

6. in the path android/app/src/main/java/com/inappmodule, open the MainApplication.kt file and adds the following lines:

package com.inappmodule

import android.app.Application
import com.facebook.react.PackageList
import com.facebook.react.ReactApplication
import com.facebook.react.ReactHost
import com.facebook.react.ReactNativeHost
import com.facebook.react.ReactPackage
import com.facebook.react.defaults.DefaultNewArchitectureEntryPoint.load
import com.facebook.react.defaults.DefaultReactHost.getDefaultReactHost
import com.facebook.react.defaults.DefaultReactNativeHost
import com.facebook.soloader.SoLoader
+ import com.nativelocalstorage.NativeLocalStoragePackage

class MainApplication : Application(), ReactApplication {

  override val reactNativeHost: ReactNativeHost =
      object : DefaultReactNativeHost(this) {
        override fun getPackages(): List<ReactPackage> =
            PackageList(this).packages.apply {
              // Packages that cannot be autolinked yet can be added manually here, for example:
              // add(MyReactNativePackage())
+              add(NativeLocalStoragePackage())
            }

        override fun getJSMainModuleName(): String = "index"

        override fun getUseDeveloperSupport(): Boolean = BuildConfig.DEBUG

        override val isNewArchEnabled: Boolean = BuildConfig.IS_NEW_ARCHITECTURE_ENABLED
        override val isHermesEnabled: Boolean = BuildConfig.IS_HERMES_ENABLED
      }

  override val reactHost: ReactHost
    get() = getDefaultReactHost(applicationContext, reactNativeHost)

  override fun onCreate() {
    super.onCreate()
    SoLoader.init(this, false)
    if (BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
      // If you opted-in for the New Architecture, we load the native entry point for this app.
      load()
    }
  }
}

iOS:

1. Run yarn install in the root folder of your project.
2. Navigate to the ios folder.
3. Run bundle install.
4. Run RCT_NEW_ARCH_ENABLED=1 bundle exec pod install (starting from 0.76, you can just run bundle exec pod install).
5. Run open <AppName>.xcworkspace to Open the Xcode Workspace
6. Right click on your App and select New Group.
7. Name the new group NativeLocalStorage
8. Select the NativeLocalStorage folder
9. Right click on the folder and select New File...
10. Select Cocoa Touch Class
11. Name the class RCTNativeLocalStorage (Make sure to select Objective-C as language)
12. Press next until you create the file.
13. From Xcode, rename the RCTNativeLocalStorage.m to RCTNativeLocalStorage.mm (notice the double m)
14. Open the RCTNativeLocalStorage.h and modify the file as follows:

#import <Foundation/Foundation.h>
+ #import <NativeLocalStorageSpec/NativeLocalStorageSpec.h>

NS_ASSUME_NONNULL_BEGIN

- @interface RCTNativeLocalStorage : NSObject
+ @interface RCTNativeLocalStorage : NSObject <NativeLocalStorageSpec>

@end

NS_ASSUME_NONNULL_END

15. Open the RCTNativeLocalStorage.mm and implement the native code as follows:

#import "RCTNativeLocalStorage.h"

@implementation RCTNativeLocalStorage

+RCT_EXPORT_MODULE(NativeLocalStorage)

+- (std::shared_ptr<facebook::react::TurboModule>)getTurboModule:(const facebook::react::ObjCTurboModule::InitParams &)params {
+ return std::make_shared<facebook::react::NativeLocalStorageSpecJSI>(params);
+}

+- (NSString *)getString:(NSString *)key {
+  return [NSUserDefaults.standardUserDefaults stringForKey:key];
+}

+- (void)setString:(NSString *)value key:(NSString *)key {
+  [NSUserDefaults.standardUserDefaults setObject:value forKey:key];
+}

@end

4. Connect with the JS

1. Run the app on your device.
   • For iOS, you can run from Xcode or you can go to the root of the project and run yarn ios
   • For Android, from the root of the project, run yarn android
2. Start metro by running yarn start
3. Open the App.tsx file
4. Replace the content with the following file.

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 */

import React from 'react';
import {
  SafeAreaView,
  StatusBar,
  StyleSheet,
  useColorScheme,
  Text,
  TextInput,
  Button,
} from 'react-native';

import { Colors } from 'react-native/Libraries/NewAppScreen';

import NativeLocalStorage from './specs/NativeLocalStorage';


function App(): React.JSX.Element {
  const isDarkMode = useColorScheme() === 'dark';
  const [value, setValue] = React.useState<string | null>(null);

  const [editingValue, setEditingValue] = React.useState<string | null>(null);

  React.useEffect(() => {
    const s = NativeLocalStorage.getString('myKey');
    setValue(s);
  }, [])

  function saveValue() {
    NativeLocalStorage.setString(editingValue || "", 'myKey');
    setValue(editingValue);
  }

  const backgroundStyle = {
    backgroundColor: isDarkMode ? Colors.darker : Colors.lighter,
  };

  return (
    <SafeAreaView style={backgroundStyle, {flex: 1}}>
      <StatusBar
        barStyle={isDarkMode ? 'light-content' : 'dark-content'}
        backgroundColor={backgroundStyle.backgroundColor}
      />

      <Text style={styles.text}>Current stored value is: {value || "No Value"}</Text>

      <TextInput placeholder={"Enter the text you want to store"} style={styles.textInput} onChangeText={setEditingValue} />

      <Button title="Save" onPress={saveValue} />

    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  text: {
    margin: 10,
    fontSize: 20
  },
  textInput: {
    margin: 10,
    height: 40,
    borderColor: 'black',
    borderWidth: 1,
    paddingLeft: 5,
    paddingRight: 5,
    borderRadius: 5
  }
});

export default App;

This is the resulting app

Android	iOS