Synchronized Array (for likes/followers) Best Practice [Firebase Swift]

Question

I\'m trying to create a basic following algorithm using Swift and Firebase. My current implementation is the following:

static func follow(user: FIRUser, use         


        

Answer 1

Thanks to Frank, I figured out a solution using runTransactionBlock. Here it is:

static func follow(user: FIRUser, userToFollow: FIRUser) {
    self.database.child("users/"+(user.uid)+"/Following").runTransactionBlock({ (currentData: FIRMutableData!) -> FIRTransactionResult in
        var value = currentData?.value as? Array<String>
        if (value == nil) {
            value = [userToFollow.uid]
        } else {
            if !(value!.contains(userToFollow.uid)) {
                value!.append(userToFollow.uid)
            }
        }
        currentData.value = value!
        return FIRTransactionResult.successWithValue(currentData)
        }) { (error, committed, snapshot) in
            if let error = error {
            print("follow - update following transaction - EXCEPTION: " + error.localizedDescription)
        }
    }
}

This adds the uid of userToFollow to the array Following of user. It can handle nil values and will initialize accordingly, as well as will disregard the request if the user is already following the uid of userToFollow. Let me know if you have any questions!

Some useful links:

1. The comments of firebase runTransactionBlock
2. The answer to Upvote/Downvote system within Swift via Firebase
3. The second link I posted above