iOS¶

If you're embedding React Native into native application, you can also integrate Async Storage module, so that both worlds will use one storage solution.

AsyncStorage can be controlled by the hosting app via the delegate on RNCAsyncStorage:

RNCAsyncStorage *asyncStorage = [bridge moduleForClass:[RNCAsyncStorage class]];
asyncStorage.delegate = self;

The protocol¶

The delegate must conform to the RNCAsyncStorageDelegate protocol:

allKeys¶

- (void)allKeys:(RNCAsyncStorageResultCallback)block;

Returns all keys currently stored. If none, an empty array is returned. Called by getAllKeys in JS.

mergeValues¶

- (void)mergeValues:(NSArray<NSString *> *)values
            forKeys:(NSArray<NSString *> *)keys
         completion:(RNCAsyncStorageResultCallback)block;

Merges values with the corresponding values stored at specified keys. Called by mergeItem and multiMerge in JS.

removeAllValues¶

- (void)removeAllValues:(RNCAsyncStorageCompletion)block;

Removes all values from the store. Called by clear in JS.

removeValuesForKeys¶

- (void)removeValuesForKeys:(NSArray<NSString *> *)keys
                 completion:(RNCAsyncStorageResultCallback)block;

Removes all values associated with specified keys. Called by removeItem and multiRemove in JS.

setValues¶

- (void)setValues:(NSArray<NSString *> *)values
          forKeys:(NSArray<NSString *> *)keys
       completion:(RNCAsyncStorageResultCallback)block;

Sets specified key-value pairs. Called by setItem and multiSet in JS.

valuesForKeys¶

- (void)valuesForKeys:(NSArray<NSString *> *)keys
           completion:(RNCAsyncStorageResultCallback)block;

Returns values associated with specified keys. Called by getItem and multiGet in JS.

passthrough¶

@optional
@property (nonatomic, readonly, getter=isPassthrough) BOOL passthrough;

Optional: Returns whether the delegate should be treated as a passthrough. This is useful for monitoring storage usage among other things. Returns NO by default.

Android¶

The recommended approach here is to use Kotlin language to leverage coroutines when accessing the storage. Java is also supported (through Kotlin interop), but the approach is more cumbersome.

Prerequisites¶

Next storage feature enabled.
Add dependency on coroutines-android in your app's build.gradle

dependencies {
  // other dependencies


  // will work with coroutines 1.3.0 and up
+ implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9"

}

Your library of choice for parsing JSON storage values (since there are strings only)

Access storage¶

Kotlin (recommended)¶

We use Coroutines to handle asynchronous code. Each method on storage is suspend method, so you need to call it from within a coroutine.

Reading value¶

suspend fun readValue(ctx: Context, keys: List<String>) {
    // get instance of the Storage by providing context object
    val asyncStorage = StorageModule.getStorageInstance(ctx)

    val entries: List<Entry> = asyncStorage.getValues(keys)
    doSomethingWithValues(entries)
}

Saving value¶

suspend fun saveValue(ctx: Context) {
    val asyncStorage = StorageModule.getStorageInstance(ctx)

    val entries = listOf(
        Entry("myKey", "myValue")
    )
    asyncStorage.setValues(entries)
}

Java¶

You can access AsyncStorage form Java, but you're still required to add Kotlin dependencies. There's no one way of accessing the data and there's more than one way to parse it.

Reading from storage¶

void readStorageValue(Context ctx, String key) {
    AsyncStorageAccess asyncStorage = StorageModule.getStorageInstance(ctx);

    BuildersKt.launch(GlobalScope.INSTANCE,
                Dispatchers.getIO(),
                CoroutineStart.DEFAULT,
                (scope, continuation) -> {
                    List<String> keys = new ArrayList<>();
                    keys.add(key);

                    Continuation<? super List<? extends Entry>> cont = new Continuation() {
                        @NotNull
                        @Override
                        public CoroutineContext getContext() {
                            return scope.getCoroutineContext();
                        }

                        @Override
                        public void resumeWith(@NotNull Object o) {
                            List<Entry> entries = (List<Entry>) o;
                            doSomethingWithEntries(entries);
                        }
                    };

                    asyncStorage.getValues(keys, cont);
                    return Unit.INSTANCE;
                });

}

Saving to storage¶

void saveStorageValue(Context ctx, String key, String value) {
  AsyncStorageAccess asyncStorage = StorageModule.getStorageInstance(ctx);

  BuildersKt.launch(GlobalScope.INSTANCE,
                Dispatchers.getIO(),
                CoroutineStart.DEFAULT,
                (scope, continuation) -> {
                    Continuation cont = new Continuation() {
                        @NotNull
                        @Override
                        public CoroutineContext getContext() {
                            return scope.getCoroutineContext();
                        }

                        @Override
                        public void resumeWith(@NotNull Object o) {}
                    };

                    List<Entry> entries = new ArrayList<>();
                    Entry entry = new Entry(key, value);
                    entries.add(entry);
                    asyncStorage.setValues(entries, cont);
                    return Unit.INSTANCE;
                });
}