feat: add viewModelInstanceProperty for nested ViewModel access

Adds two methods to ViewModelInstance:
- viewModelInstanceProperty(path) - get nested ViewModel instance
- setViewModelInstanceProperty(path, instance) - replace nested instance

Includes test example with person_databinding_test.riv

Author: mfazekas

android/src/main/java/com/margelo/nitro/rive/HybridViewModelInstance.kt

@@ -52,4 +52,18 @@ class HybridViewModelInstance(val viewModelInstance: ViewModelInstance) : Hybrid
   override fun listProperty(path: String) = getPropertyOrNull {
     HybridViewModelListProperty(viewModelInstance.getListProperty(path))
   }
+
+  override fun viewModelInstanceProperty(path: String) = getPropertyOrNull {
+    HybridViewModelInstance(viewModelInstance.getInstanceProperty(path))
+  }
+
+  override fun setViewModelInstanceProperty(path: String, instance: HybridViewModelInstanceSpec): Boolean {
+    return try {
+      val nativeInstance = (instance as HybridViewModelInstance).viewModelInstance
+      viewModelInstance.setInstanceProperty(path, nativeInstance)
+      true
+    } catch (e: ViewModelException) {
+      false
+    }
+  }
 }

example/assets/rive/person_databinding_test.riv

@@ -0,0 +1,195 @@
+import {
+  View,
+  Text,
+  StyleSheet,
+  ActivityIndicator,
+  Button,
+} from 'react-native';
+import { useEffect, useMemo, useState } from 'react';
+import {
+  Fit,
+  RiveView,
+  useRiveFile,
+  useRiveEnum,
+  type ViewModelInstance,
+  type RiveFile,
+} from '@rive-app/react-native';
+import { type Metadata } from '../helpers/metadata';
+
+export default function NestedViewModelExample() {
+  const { riveFile, isLoading, error } = useRiveFile(
+    require('../../assets/rive/person_databinding_test.riv')
+  );
+
+  return (
+    <View style={styles.container}>
+      <View style={styles.riveContainer}>
+        {isLoading ? (
+          <ActivityIndicator size="large" color="#0000ff" />
+        ) : riveFile ? (
+          <WithViewModelSetup file={riveFile} />
+        ) : (
+          <Text style={styles.errorText}>{error || 'Unexpected error'}</Text>
+        )}
+      </View>
+    </View>
+  );
+}
+
+function WithViewModelSetup({ file }: { file: RiveFile }) {
+  const viewModel = useMemo(() => file.defaultArtboardViewModel(), [file]);
+  const instance = useMemo(
+    () => viewModel?.createDefaultInstance(),
+    [viewModel]
+  );
+
+  if (!instance || !viewModel) {
+    return (
+      <Text style={styles.errorText}>
+        {!viewModel
+          ? 'No view model found'
+          : 'Failed to create view model instance'}
+      </Text>
+    );
+  }
+
+  return <NestedViewModelTest instance={instance} file={file} />;
+}
+
+function NestedViewModelTest({
+  instance,
+  file,
+}: {
+  instance: ViewModelInstance;
+  file: RiveFile;
+}) {
+  const [testResults, setTestResults] = useState<string[]>([]);
+
+  // Test 1: Path notation (like rive-react does)
+  const { value: drinkType, setValue: setDrinkType } = useRiveEnum(
+    'favDrink/type',
+    instance
+  );
+
+  useEffect(() => {
+    const results: string[] = [];
+
+    // Test 1: viewModelInstanceProperty - get nested instance
+    const nestedDrink = instance.viewModelInstanceProperty('favDrink');
+    if (nestedDrink) {
+      results.push(`✅ viewModelInstanceProperty('favDrink') returned instance`);
+      results.push(`   Instance name: ${nestedDrink.instanceName}`);
+
+      // Try to get enum property from nested instance
+      const typeFromNested = nestedDrink.enumProperty('type');
+      if (typeFromNested) {
+        results.push(`✅ nestedDrink.enumProperty('type'): ${typeFromNested.value}`);
+      } else {
+        results.push(`❌ nestedDrink.enumProperty('type') returned undefined`);
+      }
+    } else {
+      results.push(`❌ viewModelInstanceProperty('favDrink') returned undefined`);
+      results.push(`   (This file may use path notation, not ViewModel instance properties)`);
+    }
+
+    // Test 2: Direct path notation
+    const directEnum = instance.enumProperty('favDrink/type');
+    if (directEnum) {
+      results.push(`✅ enumProperty('favDrink/type'): ${directEnum.value}`);
+    } else {
+      results.push(`❌ enumProperty('favDrink/type') returned undefined`);
+    }
+
+    setTestResults(results);
+  }, [instance]);
+
+  // Test 3: useRiveEnum hook result (shown separately as it updates reactively)
+  const useRiveEnumResult = drinkType
+    ? `✅ useRiveEnum('favDrink/type'): ${drinkType}`
+    : `❌ useRiveEnum('favDrink/type'): undefined`;
+
+  return (
+    <View style={styles.content}>
+      <RiveView
+        style={styles.rive}
+        autoPlay={true}
+        dataBind={instance}
+        fit={Fit.Contain}
+        file={file}
+      />
+
+      <View style={styles.info}>
+        <Text style={styles.title}>Test Results:</Text>
+        {testResults.map((result, i) => (
+          <Text key={i} style={styles.result}>
+            {result}
+          </Text>
+        ))}
+        <Text style={styles.result}>{useRiveEnumResult}</Text>
+
+        <View style={styles.buttons}>
+          <Button title="Coffee" onPress={() => setDrinkType('Coffee')} />
+          <Button title="Tea" onPress={() => setDrinkType('Tea')} />
+        </View>
+      </View>
+    </View>
+  );
+}
+
+NestedViewModelExample.metadata = {
+  name: 'Nested ViewModel',
+  description: 'Tests viewModelInstanceProperty() for accessing nested ViewModel instances',
+} satisfies Metadata;
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    backgroundColor: '#fff',
+  },
+  riveContainer: {
+    flex: 1,
+    backgroundColor: '#f5f5f5',
+  },
+  content: {
+    flex: 1,
+  },
+  rive: {
+    flex: 1,
+    width: '100%',
+  },
+  info: {
+    padding: 16,
+    backgroundColor: '#fff',
+  },
+  title: {
+    fontSize: 16,
+    fontWeight: 'bold',
+    marginBottom: 8,
+  },
+  result: {
+    fontSize: 12,
+    fontFamily: 'monospace',
+    color: '#333',
+    marginVertical: 2,
+  },
+  label: {
+    fontSize: 14,
+    color: '#666',
+    marginTop: 12,
+  },
+  value: {
+    fontSize: 18,
+    fontWeight: 'bold',
+    color: '#333',
+  },
+  buttons: {
+    flexDirection: 'row',
+    gap: 12,
+    marginTop: 16,
+  },
+  errorText: {
+    color: 'red',
+    textAlign: 'center',
+    padding: 20,
+  },
+});

example/src/pages/NestedViewModelExample.tsx

@@ -11,3 +11,4 @@ export { default as ManyViewModels } from './ManyViewModels';
 export { default as ResponsiveLayouts } from './ResponsiveLayouts';
 export { default as SharedValueListenerExample } from './SharedValueListenerExample';
 export { default as MenuListExample } from './MenuListExample';
+export { default as NestedViewModelExample } from './NestedViewModelExample';

example/src/pages/index.ts

@@ -48,4 +48,17 @@ class HybridViewModelInstance: HybridViewModelInstanceSpec {
     guard let property = viewModelInstance?.listProperty(fromPath: path) else { return nil }
     return HybridViewModelListProperty(property: property)
   }
+
+  func viewModelInstanceProperty(path: String) throws -> (any HybridViewModelInstanceSpec)? {
+    guard let instance = viewModelInstance?.viewModelInstanceProperty(fromPath: path) else { return nil }
+    return HybridViewModelInstance(viewModelInstance: instance)
+  }
+
+  func setViewModelInstanceProperty(path: String, instance: any HybridViewModelInstanceSpec) throws -> Bool {
+    guard let hybridInstance = instance as? HybridViewModelInstance,
+          let nativeInstance = hybridInstance.viewModelInstance else {
+      return false
+    }
+    return viewModelInstance?.setViewModelInstanceProperty(fromPath: path, to: nativeInstance) ?? false
+  }
 }