`iOS crash: TextToSpeech.setDefaultRate(): Error converting JavaScript argument to Objective-C BOOL (unsupported type)`

[jorgemengibar-jpg]

Summary

On iOS, calling both Tts.setDefaultRate() and Tts.stop() causes crashes with the following errors:

setDefaultRate:

TextToSpeech.setDefaultRate(): Error while converting JavaScript argument 1
to Objective C type BOOL. Objective C type BOOL is unsupported.

stop:

TextToSpeech.stop(): Error while converting JavaScript argument 0
to Objective C type BOOL. Objective C type BOOL is unsupported.

Platform

• Platform: iOS
• react-native-tts version: (your version here)
• React Native version: (your version here)
• JS engine: Hermes
• Architecture: New Architecture enabled
• Device: (device + iOS version here)
• Build types: Debug and Release (TestFlight)

Steps to Reproduce

Minimal example:

import Tts from "react-native-tts";
import { Platform } from "react-native";

async function testTTS() {
  await Tts.getInitStatus();

  // Crashes on iOS:
  await Tts.setDefaultRate(0.5);

  // Later in the code:
  await Tts.speak("Test TTS");
  await Tts.stop(); // also crashes on iOS
}

1. Install react-native-tts
2. Run the code above on iOS with New Architecture / Hermes enabled.
3. Observe crash and error message.

Expected Behavior

• setDefaultRate() and stop() should work on iOS or at least fail gracefully without crashing.

Actual Behavior

• The app crashes at the bridge layer when converting the JS arguments to Objective-C BOOL.
• In the iOS implementation, the native signatures use pointer types like:

skipTransform:(BOOL *)skipTransform
// and for stop(...)
stop:(BOOL *)immediate

The new iOS bridge / TurboModule type system does not support BOOL * and throws the “Objective C type BOOL is unsupported” error.

Additional context

• Other libraries have hit the same issue with BOOL / BOOL * arguments when enabling New Architecture and Hermes.
• This seems to affect any method in this module that uses BOOL * parameters.

Temporary workaround

In JS, skipping these calls on iOS works around the crash:

if (Platform.OS === "android") {
  Tts.setDefaultRate(0.5);
  Tts.stop();
}

Android continues to work fine; the problem is only on iOS.

Suggested fix

Update the iOS native module to avoid BOOL * in exported methods, e.g.:

• Replace BOOL * parameters with NSNumber * or BOOL.
• Handle the value inside the method (e.g. immediate.boolValue).

Happy to test any patch or PR that removes the BOOL * usage and confirm it works with New Architecture + Hermes.

[jorgemengibar-jpg]

If you keep having the same problem just use the old architecture till they fix it.

[MarkCSmith]

This PR is possibly helpful: #278 (full disclosure: I have not tried it yet)

[richaapptrait]

I’m experiencing the same issue on iOS.

Both TextToSpeech.setDefaultRate() and TextToSpeech.stop() crash with:
“Error converting JavaScript argument to Objective-C BOOL (unsupported type)”.

Environment:

• Platform: iOS
• react-native-tts: ^4.1.1
• React Native: 0.81.5
• Expo: ~54.0.27

[danidaryaweesh]

Any update on this issue? I'm also experiencing this issue with RN 0.83

[qzl-dev]

experiencing the same issue as well.

[qzl-dev]

use this forked package https://www.npmjs.com/package/@iternio/react-native-tts
fixed the issue