react-native-firebase/docs/v2/modules/transactions.md

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2017-08-11 16:20:10 +00:00
# Transactions
?> For help on how to use firebase transactions please see the [Firebase Transaction Documentation](https://firebase.google.com/docs/reference/js/firebase.database.Reference#transaction).
### Android Implementation
The [android implementation](https://github.com/invertase/react-native-firebase/blob/master/android/src/main/java/io/invertase/firebase/database/RNFirebaseTransactionHandler.java) makes use of [Condition](https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/Condition.html) and [ReentrantLock](https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/ReentrantLock.html) locks to handle transactions across the React Native Bridge.
### iOS Implementation
The [iOS implementation](https://github.com/invertase/react-native-firebase/blob/master/ios/RNFirebase/RNFirebaseDatabase.m#L279) makes use of GCD (Grand Central Dispatch) to handle transactions across the React Native Bridge without blocking the application thread. Check out [this](https://mikeash.com/pyblog/friday-qa-2011-10-14-whats-new-in-gcd.html) post for some 'light' reading about it.
!> Transactions that receive no response from react native's JS thread within 30 seconds are automatically aborted - this value is currently not configurable - PR welcome.
## Example
```javascript
const ref = firebase.database().ref('user/posts');
ref.transaction((posts) => {
return (posts || 0) + 1;
}, (error, committed, snapshot) => {
if (error) {
console.log('Something went wrong', error);
} else if (!committed) {
console.log('Aborted'); // Returning undefined will trigger this
} else {
console.log('User posts incremented by 1');
}
console.log('User posts is now: ', snapshot.val());
});
```