Cloud Functions for Firebase: Increment Counter
10,814
Definitely! In fact, that's exactly how it's done in this code sample, although with a few small differences:
exports.countlikechange = functions.database.ref("/posts/{postid}/likes/{likeid}").onWrite((event) => {
var collectionRef = event.data.ref.parent;
var countRef = collectionRef.parent.child('likes_count');
return countRef.transaction(function(current) {
if (event.data.exists() && !event.data.previous.exists()) {
return (current || 0) + 1;
}
else if (!event.data.exists() && event.data.previous.exists()) {
return (current || 0) - 1;
}
});
});
Notably, this sample handles both an increment and a decrement case depending on whether the child node is being created or deleted.
Comments
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J. Adam Connor almost 2 years
Is it acceptable to increment a counter with a realtime database trigger using transaction?
exports.incPostCount = functions.database.ref('/threadsMeta/{threadId}/posts') .onWrite(event => { admin.database().ref('/analytics/postCount') .transaction(count => { if (count === null) { return count = 1 } else { return count + 1 } }) });