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// Copyright 2017 Google
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
import UIKit
import FirebaseDatabase
/// A class to demonstrate the Firebase Realtime Database API. This will show a number read
/// from the Database and increase or decrease it based on the buttons pressed.
class DatabaseViewController: UIViewController {
private enum Counter: Int {
case increment = 1
case decrement = -1
var intValue: Int {
return rawValue
}
}
// MARK: - Interface
/// Label to display the current value.
@IBOutlet weak var currentValue: UILabel!
// MARK: - User Actions
/// The increment button was hit.
@IBAction func incrementButtonHit(_ sender: UIButton) { changeServerValue(with: .increment) }
/// the decrement button was hit.
@IBAction func decrementButton(_ sender: UIButton) { changeServerValue(with: .decrement) }
// MARK: - Internal Helpers
/// Update the number on the server by a particular value. Note: the number passed in should only
/// be one above or below the current number.
private func changeServerValue(with type: Counter) {
let ref = Database.database().reference(withPath: Constants.databasePath)
// Update the current value of the number.
ref.runTransactionBlock { (currentData) -> TransactionResult in
guard let value = currentData.value as? Int else {
return TransactionResult.abort()
}
currentData.value = value + type.intValue
return TransactionResult.success(withValue: currentData)
}
}
// MARK: - View Controller Lifecycle
override func viewDidLoad() {
super.viewDidLoad()
// Observe the current value, and update the UI every time it changes.
let ref = Database.database().reference(withPath: Constants.databasePath)
ref.observe(.value) { [weak self] (snapshot) in
guard let value = snapshot.value as? Int else {
print("Error grabbing value from Snapshot!")
return
}
self?.currentValue.text = "\(value)"
}
}
// MARK: - Constants
private struct Constants {
static let databasePath = "magicSyncingCounter"
}
}
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