React Native's Native Module documentation for Android says that ReadableMap directly maps to a Javascript object. I assume this means that when I pass an object from Javascript to a native module, it is available as a ReadableMap.
How do I do the reverse, which is to create a dictionary (mapping string to string) in a native module and return it to Javascript via a callback?
2 Answers
You can use WritableMap to simply pass map values through callback.
@ReactMethod
public void pass(Callback cb) {
HashMap<String, String> hm = new HashMap<>();
hm.put("A", "one");
hm.put("B", "Two");
hm.put("C", "Three");
WritableMap map = new WritableNativeMap();
for (Map.Entry<String, String> entry : hm.entrySet()) {
map.putString(entry.getKey(), entry.getValue());
}
cb.invoke(map);
}
for more complex data, see this blog.
For React Native >=0.62, you can use this:
import com.facebook.react.bridge.WritableMap;
import com.facebook.react.bridge.Arguments;
@ReactMethod
public void test(Callback callback) {
WritableMap map = Arguments.createMap();
map.putString("yourKey", "yourValue");
callback.invoke(map);
}
To call the native function in React Native, do this:
import { NativeModules } from 'react-native';
NativeModules["replaceWithTheModuleName"].test(res => {
console.log(res);
})
