CODEWITHSUNDEEP
iosswiftfirebasefirebase-realtime-database
bibscy
bibscy

Reputation: 2708

Firebase. how to save data as transactions without overwriting the existing data, but updating it? Swift3

Is it possible to save data as transactions as per firebase docs, but without overwriting the whole node? I would like to know if there is any equivalent for updateChildValues when calling runTransactionBlock. The only option I see in the docs with runTransactionBlock is to overwrite the existing data at /path/somepath.
Please provide alternative or I'd appreciate your advice if I am on a wrong path here and I should not key:value to existing data.

Upvotes: 0

Views: 416

Answers (2)

niroshan
niroshan

Reputation: 181

The trick is to check the return value and if its nil append the initial value or else update it,

articleRef.runTransactionBlock({ (currentData: MutableData) -> TransactionResult in if var viewInfo = currentData.value as? [String : AnyObject] { var viewCount = viewInfo["viewCount"] as? Int ?? 0 viewCount += 1 viewInfo["viewCount"] = viewCount as AnyObject? //Set value and report transaction success currentData.value = viewInfo return TransactionResult.success(withValue: currentData) } else { //Iarticle doesnt exists, add inital value currentData.value = ["viewCount": 1] } return TransactionResult.success(withValue: currentData) }) { (error, committed, snapshot) in if let error = error { print(error.localizedDescription) } }

Upvotes: 1

Frank van Puffelen
Frank van Puffelen

Reputation: 598740

When you run a transaction, your callback/handler is invoked with the existing data in the location. So all you do is update the properties that you want modified and return that combination from your callback/handler.

There is no way to just tell the client what properties to update. But since your handler is invoked with the existing value from the location it's updating, that should not lead to inefficiencies in the code.

If you're having trouble making this work, please post a single, minimal-but-complete code snippet that reproduces the problem.

Upvotes: 2

Related Questions