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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 FirebaseStorage
class StorageViewController: UIViewController {
/// An enum describing the different states of the view controller.
private enum UIState: Equatable {
/// No image is being shown, waiting on user action.
case cleared
/// Currently downloading from Firebase.
case downloading(StorageTask)
/// The image has downloaded and should be displayed.
case downloaded(UIImage)
/// Show an error message and stop downloading.
case failed(String)
/// Equatable support for UIState.
static func ==(lhs: StorageViewController.UIState, rhs: StorageViewController.UIState) -> Bool {
switch (lhs, rhs) {
case (.cleared, .cleared): return true
case (.downloading, .downloading): return true
case (.downloaded, .downloaded): return true
case (.failed, .failed): return true
default: return false
}
}
}
/// MARK: - Properties
/// The current internal state of the view controller.
private var state: UIState = .cleared {
didSet { changeState(from: oldValue, to: state) }
}
// MARK: Interface
/// Image view to display the downloaded image.
@IBOutlet weak var imageView: UIImageView!
/// The download button.
@IBOutlet weak var downloadButton: UIButton!
/// The clear button.
@IBOutlet weak var clearButton: UIButton!
/// A visual representation of the state.
@IBOutlet weak var stateLabel: UILabel!
// MARK: - User Actions
@IBAction func downloadButtonHit(_ sender: UIButton) {
guard case .cleared = state else { return }
// Start the download.
let storage = Storage.storage()
let ref = storage.reference(withPath: Constants.downloadPath)
// TODO: Show progress bar here using proper API.
let task = ref.getData(maxSize: Constants.maxSize) { [unowned self] (data, error) in
guard let data = data else {
self.state = .failed("Error downloading: \(error!.localizedDescription)")
return
}
// Create a UIImage from the PNG data.
guard let image = UIImage(data: data) else {
self.state = .failed("Unable to initialize image with data downloaded.")
return
}
self.state = .downloaded(image)
}
// The completion block above could be run before this line in some situations. If that's the
// case, we don't need to do anything else and can return.
if case .downloaded = state { return }
// Set the state to downloading!
state = .downloading(task)
}
@IBAction func clearButtonHit(_ sender: UIButton) {
guard case .downloaded = state else { return }
state = .cleared
}
// MARK: - State Management
/// Changing from old state to new state.
private func changeState(from oldState: UIState, to newState: UIState) {
if oldState == newState { return }
switch (oldState, newState) {
// Regular state, start downloading the image.
case (.cleared, .downloading(_)):
// TODO: Update the UI with a spinner? Progress update?
stateLabel.text = "State: Downloading..."
// Download complete, ensure the download button is still off and enable the clear button.
case (_, .downloaded(let image)):
imageView.image = image
stateLabel.text = "State: Image downloaded!"
// Clear everything and reset to the original state.
case (_, .cleared):
imageView.image = nil
stateLabel.text = "State: Pending download"
// An error occurred.
case (_, .failed(let error)):
stateLabel.text = "State: \(error)"
// For now, as the default, throw a fatal error because it's an unexpected state. This will
// allow us to catch it immediately and add the required action or fix the bug.
default:
fatalError("Programmer error! Tried to go from \(oldState) to \(newState)")
}
}
// MARK: - Constants
/// Internal constants for this class.
private struct Constants {
/// The image name to download. Can comment this out and replace it with the other below it as
/// part of the demo. Ensure that Storage has an image uploaded to this path for this to
/// function properly.
static let downloadPath = "YOUR_IMAGE_NAME.jpg"
static let maxSize: Int64 = 1024 * 1024 * 10 // ~10MB
}
}
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