delegate method does not get called second time - swift

I am building a simple currency converter app. When ViewController gets opened it calls a function from CoinManager.swift:
class ViewController: UIViewController {
var coinManager = CoinManager()
override func viewDidLoad() {
super.viewDidLoad()
coinManager.delegate = self
coinManager.getCoinPrice(for: "AUD", "AZN", firstCall: true)
}
...
}
CoinManager.swift:
protocol CoinManagerDelegate {
func didUpdatePrice(price1: Double, currency1: String, price2: Double, currency2: String)
func tellTableView(descriptions: [String], symbols: [String])
func didFailWithError(error: Error)
}
struct CoinManager {
var delegate: CoinManagerDelegate?
let baseURL = "https://www.cbr-xml-daily.ru/daily_json.js"
func getCoinPrice (for currency1: String,_ currency2: String, firstCall: Bool) {
if let url = URL(string: baseURL) {
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (data, response, error) in
if error != nil {
self.delegate?.didFailWithError(error: error!)
return
}
if let safeData = data {
if let coinData = self.parseJSON(safeData) {
if firstCall {
var descriptions = [""]
let listOfCoins = Array(coinData.keys)
for key in listOfCoins {
descriptions.append(coinData[key]!.Name)
}
descriptions.removeFirst()
self.delegate?.tellTableView(descriptions: descriptions, symbols: listOfCoins)
}
if let coinInfo1 = coinData[currency1] {
let value1 = coinInfo1.Value
if let coinInfo2 = coinData[currency2] {
let value2 = coinInfo2.Value
//this line does not do anything the second time I call getCoinPrice:
self.delegate?.didUpdatePrice(price1: value1, currency1: currency1, price2: value2, currency2: currency2)
//And this one does work
print("delegate:\(currency1)")
} else {
print("no name matches currency2")
}
} else {
print("no name matches currency1")
}
}
}
}
task.resume()
}
}
func ParseJSON....
}
The method it calls (ViewController.swift):
extension ViewController: CoinManagerDelegate {
func didUpdatePrice(price1: Double, currency1: String, price2: Double, currency2: String) {
print("didUpdatePrice called")
DispatchQueue.main.async {
let price1AsString = String(price1)
let price2AsString = String(price2)
self.leftTextField.text = price1AsString
self.rightTextField.text = price2AsString
self.leftLabel.text = currency1
self.rightLabel.text = currency2
}
}
...
}
and finally, CurrencyViewController.swift:
var coinManager = CoinManager()
#IBAction func backButtonPressed(_ sender: UIBarButtonItem) {
dismiss(animated: true, completion: nil)
coinManager.getCoinPrice(for: "USD", "AZN", firstCall: false)
}
So when I launch the app i get following in my debug console:
didUpdatePrice called
delegate:AUD
And when I call getCoinPrice() from CurrencyViewController the delegate method does not get called. I know that my code goes through the delegate function line as I get this in debug console:
delegate:USD
I just can't wrap my head around it. The delegate method does not work when gets called second time. Even though it is called by the same algorithm

It's because you're creating a new object of CoinManager in CurrencyViewController where the delegate is not set. So you've to set the delegate every time you create a new instance of CoinManager.
#IBAction func backButtonPressed(_ sender: UIBarButtonItem) {
dismiss(animated: true, completion: nil)
coinManager.delegate = self
coinManager.getCoinPrice(for: "USD", "AZN", firstCall: false)
}
Update: So, the above solution would require for you to make the delegate conformance in CurrencyViewController. If you're looking for an alternate solution you should probably pass the instance of coinManager in ViewController to CurrencyViewController. For that here are the things you need to update.
In CurrencyViewController:
class CurrencyViewController: UIViewController {
var coinManager: CoinManager! // you can optional unwrap if you intent to use CurrencyViewController without coinManager
//...
And in ViewController:
currencyViewController.coinManager = coinManager // passing the instance of coinManager

Can you share the full code of CoinManager? I see this part
if firstCall {
...
}
Maybe some block logic here or unhandled cases? And can you share the full code of protocol?
Also try to print something before this code:
if error != nil {
self.delegate?.didFailWithError(error: error!)
return
}

Related

How to made a UIViewController class reusable to pass data back to a viewController that calls it

I was using the code from the following site
https://www.hackingwithswift.com/example-code/media/how-to-scan-a-qr-code
The code works perfectly, the code can be viewed by accessing the link above.
It was a code that capture a QRCode/BarCode from camera and convert it to string.
The part of the the code that shows the string is:
func found(code: String) {
print(code)
}
After that the code string is "printed", the code calls "dismiss" and return to the previous UIViewController.
I want to get the "code" string and get the data to the previous UIViewController.
The only way that I am able to do that now is using the following code:
func found(code: String) {
print("code: \(code)")
ResenhaEquideoIdentificaAnimal1Controller.shared.microchipAnimalTextField.text = code
}
But this code only works if the code is called by the "ResenhaEquideoIdentificaAnimal1Controller" class.
I use the following code to call the new UIViewController inside the "ResenhaEquideoIdentificaAnimal1Controller" class using a UIButton.
let myScannerViewController = MyScannerViewController()
present(myScannerViewController, animated: true, completion: nil)
How can I made this class reusable to be able to call the "MyScannerViewController" class
and send data back to the view that calls it?
You want to use a "delegate patten", that is, when the code is found or something went wrong, you delegate the functionality to some other party to deal with it.
For example, you could modify the existing example to add support for a simple delegate...
import AVFoundation
import UIKit
protocol ScannerDelegate: AnyObject {
func scanner(_ controller: ScannerViewController, didDiscoverCode code: String)
func failedToScanner(_ controller: ScannerViewController)
}
class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
weak var scannerDelegate: ScannerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.black
captureSession = AVCaptureSession()
guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
let videoInput: AVCaptureDeviceInput
do {
videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
} catch {
return
}
if (captureSession.canAddInput(videoInput)) {
captureSession.addInput(videoInput)
} else {
failed()
return
}
let metadataOutput = AVCaptureMetadataOutput()
if (captureSession.canAddOutput(metadataOutput)) {
captureSession.addOutput(metadataOutput)
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
metadataOutput.metadataObjectTypes = [.qr]
} else {
failed()
return
}
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
captureSession.startRunning()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if (captureSession?.isRunning == false) {
captureSession.startRunning()
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if (captureSession?.isRunning == true) {
captureSession.stopRunning()
}
}
private func failed() {
captureSession = nil
scannerDelegate?.failedToScanner(self)
}
private func didFind(code: String) {
scannerDelegate?.scanner(self, didDiscoverCode: code)
}
override var prefersStatusBarHidden: Bool {
return true
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
return .portrait
}
// MARK: AVCaptureMetadataOutputObjectsDelegate
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
captureSession.stopRunning()
if let metadataObject = metadataObjects.first {
guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
guard let stringValue = readableObject.stringValue else { return }
AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
didFind(code: stringValue)
}
}
}
When you want to scan something, your calling view controller could adopt the protocol...
extension ViewController: ScannerDelegate {
func failedToScanner(_ controller: ScannerViewController) {
controller.dismiss(animated: true) {
let ac = UIAlertController(title: "Scanning not supported", message: "Your device does not support scanning a code from an item. Please use a device with a camera.", preferredStyle: .alert)
ac.addAction(UIAlertAction(title: "OK", style: .default))
self.present(ac, animated: true)
}
}
func scanner(_ controller: ScannerViewController, didDiscoverCode code: String) {
codeLabel.text = code
controller.dismiss(animated: true)
}
}
and when you wanted to present the scanner view controller, you would simply set the view controller as the delegate...
let controller = ScannerViewController()
controller.scannerDelegate = self
present(controller, animated: true)
The great thing about this is, you could easily reject the code if you weren't interested in simply by modifying the delegate workflow

How do I pass a scanned barcode ID from first view controller to second View Controller's UILabel?

This is the barcode scanning tutorial I used in my program, so that you have a lot more context when you read my code: Link
Here is what my program does so far: Essentially, when I scan an item's barcode with my phone, the UIAlert pops up with the barcode ID displayed and a button prompting the user to open the "Results" page. This is all fine and good, but how do I pass that same scanned barcode ID into a label on the Result's page? I have been stuck on this for 2 days now, even though it seems like such an easy task.
Any help is much appreciated <3
Here is my relevant code:
ProductCatalog.plist ->
Link to Image
Scanner_ViewController.swift (first View Controller) ->
import UIKit
import AVFoundation
class Scanner_ViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate, ScannerDelegate
{
private var scanner: Scanner?
override func viewDidLoad()
{
super.viewDidLoad()
self.scanner = Scanner(withDelegate: self)
guard let scanner = self.scanner else
{
return
}
scanner.requestCaptureSessionStartRunning()
}
override func didReceiveMemoryWarning()
{
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// Mark - AVFoundation delegate methods
public func metadataOutput(_ output: AVCaptureMetadataOutput,
didOutput metadataObjects: [AVMetadataObject],
from connection: AVCaptureConnection)
{
guard let scanner = self.scanner else
{
return
}
scanner.metadataOutput(output,
didOutput: metadataObjects,
from: connection)
}
// Mark - Scanner delegate methods
func cameraView() -> UIView
{
return self.view
}
func delegateViewController() -> UIViewController
{
return self
}
func scanCompleted(withCode code: String)
{
print(code)
showAlert_Success(withTitle: (code))
}
private func showAlert_Success(withTitle title: String)
{
let alertController = UIAlertController(title: title, message: "Product has been successfully scanned", preferredStyle: .alert)
// programatically segue to the next view controller when the UIAlert pops up
alertController.addAction(UIAlertAction(title:"Get Results", style: .default, handler:{ action in self.performSegue(withIdentifier: "toAnalysisPage", sender: self) }))
present(alertController, animated: true)
}
}
Scanner.Swift (accompanies Scanner_ViewController.swift)->
import Foundation
import UIKit
import AVFoundation
protocol ScannerDelegate: class
{
func cameraView() -> UIView
func delegateViewController() -> UIViewController
func scanCompleted(withCode code: String)
}
class Scanner: NSObject
{
public weak var delegate: ScannerDelegate?
private var captureSession : AVCaptureSession?
init(withDelegate delegate: ScannerDelegate)
{
self.delegate = delegate
super.init()
self.scannerSetup()
}
private func scannerSetup()
{
guard let captureSession = self.createCaptureSession()
else
{
return
}
self.captureSession = captureSession
guard let delegate = self.delegate
else
{
return
}
let cameraView = delegate.cameraView()
let previewLayer = self.createPreviewLayer(withCaptureSession: captureSession,
view: cameraView)
cameraView.layer.addSublayer(previewLayer)
}
private func createCaptureSession() -> AVCaptureSession?
{
do
{
let captureSession = AVCaptureSession()
guard let captureDevice = AVCaptureDevice.default(for: .video) else
{
return nil
}
let deviceInput = try AVCaptureDeviceInput(device: captureDevice)
let metaDataOutput = AVCaptureMetadataOutput()
// add device input
if captureSession.canAddInput(deviceInput) && captureSession.canAddOutput(metaDataOutput)
{
captureSession.addInput(deviceInput)
captureSession.addOutput(metaDataOutput)
guard let delegate = self.delegate,
let viewController = delegate.delegateViewController() as? AVCaptureMetadataOutputObjectsDelegate else
{
return nil
}
metaDataOutput.setMetadataObjectsDelegate(viewController,
queue: DispatchQueue.main)
metaDataOutput.metadataObjectTypes = self.metaObjectTypes()
return captureSession
}
}
catch
{
// handle error
}
return nil
}
private func createPreviewLayer(withCaptureSession captureSession: AVCaptureSession,
view: UIView) -> AVCaptureVideoPreviewLayer
{
let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
return previewLayer
}
private func metaObjectTypes() -> [AVMetadataObject.ObjectType]
{
return [.qr,
.code128,
.code39,
.code39Mod43,
.code93,
.ean13,
.ean8,
.interleaved2of5,
.itf14,
.pdf417,
.upce
]
}
public func metadataOutput(_ output: AVCaptureMetadataOutput,
didOutput metadataObjects: [AVMetadataObject],
from connection: AVCaptureConnection)
{
self.requestCaptureSessionStopRunning()
guard let metadataObject = metadataObjects.first,
let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject,
let scannedValue = readableObject.stringValue,
let delegate = self.delegate
else
{
return
}
delegate.scanCompleted(withCode: scannedValue)
}
public func requestCaptureSessionStartRunning()
{
self.toggleCaptureSessionRunningState()
}
public func requestCaptureSessionStopRunning()
{
self.toggleCaptureSessionRunningState()
}
private func toggleCaptureSessionRunningState()
{
guard let captureSession = self.captureSession
else
{
return
}
if !captureSession.isRunning
{
captureSession.startRunning()
}
else
{
captureSession.stopRunning()
}
}
}
Analysis_ViewController.swift (second view controller) ->
Right now, the forKey: has been hard-coded to item ID 8710908501708 because I have no idea how to actually pass camera-scanned ID's into the second View Controller :/
import UIKit
class Analysis_ViewController: UIViewController
{
#IBOutlet weak var productTitle: UILabel!
func getData()
{
let path = Bundle.main.path(forResource:"ProductCatalog", ofType: "plist")
let dict:NSDictionary = NSDictionary(contentsOfFile: path!)!
if (dict.object(forKey: "8710908501708" as Any) != nil)
{
if let levelDict:[String : Any] = dict.object(forKey: "8710908501708" as Any) as? [String : Any]
{
// use a for loop to iterate through all the keys and values in side the "Levels" dictionary
for (key, value) in levelDict
{
// if we find a key named whatever we care about, we can print out the value
if (key == "name")
{
productTitle.text = (value as! String)
}
}
}
}
}
// listing the better options that are safer in comparison to the scanned product image
override func viewDidLoad()
{
super.viewDidLoad()
getData()
}
}
Do you have a variable to hold the scanned ID in your view controllers? If not, you can add var itemID: String? to both Scanner_ViewController and Analysis_ViewController.
Then in your func where you get the scanned code, you can set it to the variable.
func scanCompleted(withCode code: String) {
print(code)
itemID = code // Saves the scanned code to your var
showAlert_Success(withTitle: (code))
}
For passing data to another view controller via segue, you might want to look into this UIViewController method for segues: documentation here. This answer also might help.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "toAnalysisPage" {
if let viewController = segue.destination as? Analysis_ViewController {
viewController.itemID = itemID
}
}
}

didInititate method for Spotify IOS SDK is not calling even though called sessionManager.initiateSession()

I'm going through Spotify's authentication process and am requesting the scopes appRemoteControl for my app to control music and userReadCurrentlyPlaying for current song. I set up everything from the SPTConfiguration, SPTSessionManager, and SPTAppRemote, and their required delegate methods (SPTAppRemoteDelegate, SPTSessionManagerDelegate, SPTAppRemotePlayerStateDelegate) as well as initiating a session with the requested scopes whenever the user presses a button but I can't get the method
func sessionManager(manager: SPTSessionManager, didInitiate session: SPTSession) {
appRemote.connectionParameters.accessToken = session.accessToken
appRemote.connect()
print(session.accessToken)
}
to trigger. The authentication process fully works as it goes into my spotify app and returns back to my application and plays a song from the configuration.playURI = "" , however, the method above never is called. I followed the spotify demo project but still does not work. Here is my full code
class LogInViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
let spotifyClientID = Constants.clientID
let spotifyRedirectURL = Constants.redirectURI
let tokenSwap = "https://***********.glitch.me/api/token"
let refresh = "https://***********.glitch.me/api/refresh_token"
lazy var configuration: SPTConfiguration = {
let configuration = SPTConfiguration(clientID: spotifyClientID, redirectURL: URL(string: "Lyrically://callback")!)
return configuration
}()
lazy var sessionManager: SPTSessionManager = {
let manager = SPTSessionManager(configuration: configuration, delegate: self)
if let tokenSwapURL = URL(string: tokenSwap), let tokenRefreshURL = URL(string: refresh) {
self.configuration.tokenSwapURL = tokenSwapURL
self.configuration.tokenRefreshURL = tokenRefreshURL
self.configuration.playURI = ""
}
return manager
}()
lazy var appRemote: SPTAppRemote = {
let appRemote = SPTAppRemote(configuration: configuration, logLevel: .debug)
appRemote.delegate = self
return appRemote
}()
#IBAction func logIn(_ sender: UIButton) {
let requestedScopes: SPTScope = [.appRemoteControl, .userReadCurrentlyPlaying]
sessionManager.initiateSession(with: requestedScopes, options: .default)
}
}
extension LogInViewController: SPTAppRemotePlayerStateDelegate {
func playerStateDidChange(_ playerState: SPTAppRemotePlayerState) {
print("state changed")
}
}
extension LogInViewController: SPTAppRemoteDelegate {
func appRemoteDidEstablishConnection(_ appRemote: SPTAppRemote) {
print("connected")
appRemote.playerAPI?.delegate = self
appRemote.playerAPI?.subscribe(toPlayerState: { (success, error) in
if let error = error {
print("Error subscribing to player state:" + error.localizedDescription)
}
})
}
func appRemote(_ appRemote: SPTAppRemote, didFailConnectionAttemptWithError error: Error?) {
print("failed")
}
func appRemote(_ appRemote: SPTAppRemote, didDisconnectWithError error: Error?) {
print("disconnected")
}
}
extension LogInViewController: SPTSessionManagerDelegate {
func sessionManager(manager: SPTSessionManager, didInitiate session: SPTSession) {
appRemote.connectionParameters.accessToken = session.accessToken
appRemote.connect()
print(session.accessToken)
}
func sessionManager(manager: SPTSessionManager, didFailWith error: Error) {
print("failed",error)
}
}
Figured it out. Had to get a hold of the sessionManager from the LogInViewController by making an instance of it
lazy var logInVC = LogInViewController()
then added this line of code into the openURLContexts method in scene delegate
func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>) {
print("Opened url")
guard let url = URLContexts.first?.url else {
return
}
logInVC.sessionManager.application(UIApplication.shared, open: url, options: [:])
}

How to catch a fatalError caused by during a UITest?

The UITest in question launches the app, taps a cell which pushes the Screen to be tested and then fails with a fatalError() when i make a change that i expect will call a fatalError().
How can i catch the fatalError on the UITest and use it to report that the UITest has failed?
Here is the UITest:
class ConcreteFoodScreenUITests: XCTestCase
{
let app = XCUIApplication()
override func setUpWithError() throws {
continueAfterFailure = false
app.launch()
}
func testPathToConcreteFoodScreen() throws {
//Tap Concrete Cell in FoodDashboard to go to the ConcreteFoodScreen
XCTAssertTrue(app.otherElements["FoodDashboard"].exists)
app.scrollViews.otherElements.tables.staticTexts["100 g, 100cal, P: 90g, F: 80g, C: 70g"].tap()
//ConcreteFoodScreen
XCTAssertTrue(app.otherElements["ConcreteFoodScreen"].exists)
app.tables.cells.containing(.staticText, identifier:"Scale").children(matching: .textField).element.tap()
app.keys["5"].tap() //FIXME: Crashes with a Fatal Error
}
}
Here is the code that is being triggered that i want to know about:
class ScaleCellTextField: SWDecimalTextField {
//there is more code here but not relevant
func updateFoodEntry() {
fatalError()
// if let scale = Double(self.text!) {
// concreteFood.scale = scale
// }
}
}
You can see that i commented out some code here to get it working.
I'm afraid you can't. FatalError() ends your app's process, so I'm not sure you can catch this kind of event.
EDIT:
But...
You can use our dear good old Darwin Notifications... In order to add create a communication channel between your apps : the tested app and the tester app.
You'll need to add a file to both your targets:
typealias NotificationHandler = () -> Void
enum DarwinNotification : String {
case fatalError
}
class DarwinNotificationCenter {
let center: CFNotificationCenter
let prefix: String
var handlers = [String:NotificationHandler]()
init(prefix: String = "com.stackoverflow.answer.") {
center = CFNotificationCenterGetDarwinNotifyCenter()
self.prefix = prefix
}
var unsafeSelf: UnsafeMutableRawPointer {
return Unmanaged.passUnretained(self).toOpaque()
}
deinit {
CFNotificationCenterRemoveObserver(center, unsafeSelf, nil, nil)
}
func notificationName(for identifier: String) -> CFNotificationName {
let name = prefix + identifier
return CFNotificationName(name as CFString)
}
func identifierFrom(name: String) -> String {
if let index = name.range(of: prefix)?.upperBound {
return String(name[index...])
}
else {
return name
}
}
func handleNotification(name: String) {
let identifier = identifierFrom(name: name)
if let handler = handlers[identifier] {
handler()
}
}
func postNotification(for identifier: String) {
let name = notificationName(for: identifier)
CFNotificationCenterPostNotification(center, name, nil, nil, true)
}
func registerHandler(for identifier: String, handler: #escaping NotificationHandler) {
handlers[identifier] = handler
let name = notificationName(for: identifier)
CFNotificationCenterAddObserver(center,
unsafeSelf,
{ (_, observer, name, _, _) in
if let observer = observer, let name = name {
let mySelf = Unmanaged<DarwinNotificationCenter>.fromOpaque(observer).takeUnretainedValue()
mySelf.handleNotification(name: name.rawValue as String)
}
},
name.rawValue,
nil,
.deliverImmediately)
}
func unregisterHandler(for identifier: String) {
handlers[identifier] = nil
CFNotificationCenterRemoveObserver(center, unsafeSelf, notificationName(for: identifier), nil)
}
}
extension DarwinNotificationCenter {
func postNotification(for identifier: DarwinNotification) {
postNotification(for: identifier.rawValue)
}
func registerHandler(for identifier: DarwinNotification, handler: #escaping NotificationHandler) {
registerHandler(for: identifier.rawValue, handler: handler)
}
func unregisterHandler(for identifier: DarwinNotification) {
unregisterHandler(for: identifier.rawValue)
}
}
Then, simply, in your tested application:
#IBAction func onTap(_ sender: Any) {
// ... Do what you need to do, and instead of calling fatalError()
DarwinNotificationCenter().postNotification(for: .fatalError)
}
To catch it in your test, just do the following:
// This is the variable you'll update when notified
var fatalErrorOccurred = false
// We need a dispatch group to wait for the notification to be caught
let waitingFatalGroup = DispatchGroup()
waitingFatalGroup.enter()
let darwinCenter = DarwinNotificationCenter()
// Register the notification
darwinCenter.registerHandler(for: .fatalError) {
// Update the local variable
fatalErrorOccurred = true
// Let the dispatch group you're done
waitingFatalGroup.leave()
}
// Don't forget to unregister
defer {
darwinCenter.unregisterHandler(for: .fatalError)
}
// Perform you tests, here just a tap
app.buttons["BUTTON"].tap()
// Wait for the group the be left or to time out in 3 seconds
let _ = waitingFatalGroup.wait(timeout: .now() + 3)
// Check on the variable to know whether the notification has been received
XCTAssert(fatalErrorOccurred)
And that's it...
Disclaimer: You should not use testing code within your production code, so the use of DarwinNotification should not appear in production. Usually I use compilation directive to only have it in my code in debug or tests, not in release mode.

What is a good way to handle async requests in ReSwift/Redux

To make an asynchronous request a middleware is used in this case, it returns an error after a fixed amount of time.
The app state is properly updated the subscriber view controller presents the error.
On the next instance however this subscriber view controller is presented, it finds the error in the state - which is actually the error from the previous request and displays the error message before even the request is fired.
How to go about handling this case in ReSwift/Redux?
Store
let store = Store(
reducer: appReducer,
state: AppState(),
middleware: [requestMiddleware]
)
State
struct AppState: StateType {
var isRequestInProgress = false
var result: Result<Bool, NSError>?
}
Actions
struct RequestAction: Action {}
struct ReceiveAction: Action {}
struct ErrorAction: Action {
let error: NSError
}
Middleware
let requestMiddleware: Middleware<Any> = { dispatch, getState in
return { next in
return { action in
switch action {
case is RequestAction:
DispatchQueue.main.asyncAfter(deadline: .now() + 2, execute: {
store.dispatch(ErrorAction(error: NSError(domain: "", code: -1, userInfo: nil)))
})
default:
break
}
return next(action)
}
}
}
Reducer
func appReducer(action: Action, state: AppState?) -> AppState {
var state = state ?? AppState()
switch action {
case is RequestAction:
state.isRequestInProgress = true
case let action as ErrorAction:
state.isRequestInProgress = false
state.result = .failure(action.error)
default: break
}
return state
}
The app
class ViewController: UIViewController {
#IBAction func presentControllerB(_ sender: Any) {
guard let viewController = storyboard?.instantiateViewController(withIdentifier: "ViewControllerB") else {
return
}
present(viewController, animated: true)
}
}
class ViewControllerB: UIViewController, StoreSubscriber {
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
store.subscribe(self)
}
override func viewWillDisappear(_ animated: Bool) {
store.unsubscribe(self)
super.viewWillDisappear(animated)
}
func newState(state: AppState) {
showActivity(state.isRequestInProgress)
switch state.result {
case .none:
break
case .some(.success(_)):
break
case .some(.failure(let error)):
presentError(error)
dismiss(animated: true)
}
}
#IBAction func request(_ sender: Any) {
store.dispatch(RequestAction())
}
private func showActivity(_ show: Bool) {}
private func presentError(_ error: Error) {
print("Error")
}
}