Keep languages constants for faster I18n init

android/src/main/java/com/AlexanderZaytsev/RNI18n/RNI18nModule.java

@@ -10,7 +10,9 @@ import com.facebook.react.bridge.ReactContextBaseJavaModule;
 import com.facebook.react.bridge.ReactMethod;
 import com.facebook.react.bridge.WritableArray;
 
+import java.util.HashMap;
 import java.util.Locale;
+import java.util.Map;
 
 public class RNI18nModule extends ReactContextBaseJavaModule {
 
@@ -39,20 +41,32 @@ public class RNI18nModule extends ReactContextBaseJavaModule {
     return builder.toString();
   }
 
+  private WritableArray getLocaleList() {
+    LocaleList locales = Build.VERSION.SDK_INT >= Build.VERSION_CODES.N
+      ? getReactApplicationContext().getResources().getConfiguration().getLocales()
+      : new LocaleList(getReactApplicationContext().getResources().getConfiguration().locale);
+
+    WritableArray array = Arguments.createArray();
+
+    for (int i = 0; i < locales.size(); i++) {
+      array.pushString(this.toLanguageTag(locales.get(i)));
+    }
+
+    return array;
+  }
+
+  @Override
+  public Map<String, Object> getConstants() {
+    HashMap<String, Object> constants = new HashMap<String,Object>();
+    constants.put("languages", this.getLocaleList());
+
+    return constants;
+  }
+
   @ReactMethod
   public void getLanguages(Promise promise) {
     try {
-      LocaleList locales = Build.VERSION.SDK_INT >= Build.VERSION_CODES.N
-        ? getReactApplicationContext().getResources().getConfiguration().getLocales()
-        : new LocaleList(getReactApplicationContext().getResources().getConfiguration().locale);
-
-      WritableArray languages = Arguments.createArray();
-
-      for (int i = 0; i < locales.size(); i++) {
-        languages.pushString(this.toLanguageTag(locales.get(i)));
-      }
-
-      promise.resolve(languages);
+      promise.resolve(this.getLocaleList());
     } catch (Exception e) {
       promise.reject(e);
     }

example/screen.js

@@ -1,7 +1,9 @@
 // @ flow
 
 import React, { Component } from 'react';
-import { getLanguages } from 'react-native-i18n';
+// import { languages, getLanguages } from 'react-native-i18n';
+import { NativeModules } from 'react-native';
+const { getLanguages, languages } = NativeModules.RNI18n;
 
 import {
   Platform,
@@ -23,7 +25,14 @@ export default class extends Component {
   render() {
     return (
       <ScrollView style={styles.container}>
-        <Text style={styles.title}>Methods</Text>
+        <Text style={styles.title}>Internal constants</Text>
+
+        <View style={styles.line}>
+          <Text style={styles.label}>languages: </Text>
+          <Text>{JSON.stringify(languages)}</Text>
+        </View>
+
+        <Text style={styles.title}>Internal methods</Text>
 
         <View style={styles.line}>
           <Text style={styles.label}>getLanguages (Promise): </Text>
@@ -48,6 +57,7 @@ const styles = StyleSheet.create({
   },
   line: {
     flexDirection: 'row',
+    marginBottom: 16,
   },
   label: {
     fontWeight: '700',

index.js

@@ -6,6 +6,7 @@ const { RNI18n } = NativeModules;
 
 // I18n.locale = RNI18n.language;
 
-export const getLanguages = RNI18n.getLanguages;
+// export const getLanguages = RNI18n.getLanguages;
+// export const languages = RNI18n.languages;
 
 export default I18n;

ios/RNI18n.m

@@ -15,15 +15,21 @@ RCT_EXPORT_MODULE();
   return languageTags;
 }
 
-RCT_EXPORT_METHOD(getLanguages:(RCTPromiseResolveBlock)resolve
-                  rejecter:(__unused RCTPromiseRejectBlock)reject) {
+- (NSArray *)getPreferredLanguages {
   NSArray *preferredLanguages = [NSLocale preferredLanguages];
 
-  resolve(
-    [[[UIDevice currentDevice] systemVersion] floatValue] >= 9
-      ? preferredLanguages
-      : [self toLanguageTags:preferredLanguages]
-  );
+  return [[[UIDevice currentDevice] systemVersion] floatValue] >= 9
+    ? preferredLanguages
+    : [self toLanguageTags:preferredLanguages];
+}
+
+- (NSDictionary *)constantsToExport {
+  return @{ @"languages": [self getPreferredLanguages] };
+}
+
+RCT_EXPORT_METHOD(getLanguages:(RCTPromiseResolveBlock)resolve
+                  rejecter:(__unused RCTPromiseRejectBlock)reject) {
+  resolve([self getPreferredLanguages]);
 }
 
 @end