Swift 3.2 iOS -How to Increment a NSNumber for Firebase MutableData Object?

Question

In Swift I understand NSNumbers are containers that contain scalar numbers.

InFirebase you can send NSNumbers to the database but not Ints.

I'm using Firebase Transactions for a number of likes/upvotes and I need to increase the number of times a user presses the upvote button.

Here's my code to send the data to Firebase:

likesRef?.runTransactionBlock({
       (currentData: MutableData) -> TransactionResult in

       var value = currentData.value as? NSNumber

       if value == nil{
           value = 0
       }

       let one: NSNumber = 1

       currentData.value = value! += one //error is here

       return TransactionResult.success(withValue: currentData)

I keep getting error:

Binary operator '+=' cannot be applied to two 'NSNumber' operands

The problem is I'm passing a Firebase MutableData type to the success(withValue: ) method and not the NSNumber value itself. I can't use NSNumber.intValue because Firebase doesn't accept Ints.

How can I increment two NSNumbers together to send to to Firebase as part of a MutableData object?

Answer 1

Try this:

let newValue: Int

if let existingValue = (currentData.value as? NSNumber)?.intValue {
    newValue = existingValue + 1
} else {
    newValue = 1
}

currentData.value = NSNumber(value: newValue)