36 lines
1.7 KiB
Markdown
36 lines
1.7 KiB
Markdown
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# Transactions
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?> 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).
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### Android Implementation
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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.
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### iOS Implementation
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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.
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!> 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.
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## Example
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```javascript
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const ref = firebase.database().ref('user/posts');
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ref.transaction((posts) => {
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return (posts || 0) + 1;
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}, (error, committed, snapshot) => {
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if (error) {
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console.log('Something went wrong', error);
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} else if (!committed) {
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console.log('Aborted'); // Returning undefined will trigger this
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} else {
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console.log('User posts incremented by 1');
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}
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console.log('User posts is now: ', snapshot.val());
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});
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```
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