Synchronous Authentication SwiftUI - ios

I am making an iOS app using SwiftUI that requires login. When the create account button is pressed, the action triggers a function in my NetworkManager class that sends the inputed email and password as a post request and receives the appropriate data back for authentication. It then uses the received data to determine whether the credentials are valid
My issue is that it runs the code that verifies the inputed credentials against the API response before the response is actually received. Consequently, the result is the same each time.
Button(action: {
self.networkManager.signUp(email: self.inputEmail, password: self.inputPassword)
// These if statements run before the above line is executed
if self.networkManager.signUpResponse.code == nil {
// SUCCESSFUL REGISTRATION
ProgressHUD.showSuccess("Account Successfully Created!")
UserDefaults.standard.set(true, forKey: "LoggedIn")
self.showingWelcomePage = false
}
if self.networkManager.signUpResponse.code == 201 {
// REGISTRATION FAILED
ProgressHUD.showError("This account already exists", interaction: false)
}
}) {
Text("Create Account")
.font(.headline)
}
I have tried using DispatchQueue.main.async() or creating my own thread, however nothing seems to work. I need to find a way to pause the main thread in order to wait for this line of code to execute before proceeding without using DispatchQueue.main.sync() as this results in deadlock and program crash.
Here is the code for the function that makes the post request to the API
class NetworkManager: ObservableObject {
#Published var signUpResponse = AccountResults()
func signUp(email: String, password: String) {
if let url = URL(string: SignUpAPI) {
let session = URLSession.shared
let bodyData = ["school": "1",
"email": email,
"password": password]
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.httpBody = try! JSONSerialization.data(withJSONObject: bodyData)
let task = session.dataTask(with: request) { (data, response, error) in
if error == nil {
let decoder = JSONDecoder()
if let safeData = data {
do {
let results = try decoder.decode(AccountResults.self, from: safeData)
DispatchQueue.main.async {
self.signUpResponse = results
}
} catch {
print(error)
}
}
}
}
task.resume()
}
}
}
Thanks in advance!

Try it:
func signUp(email: String, password: String, completion: #escaping((Error?, YourResponse?) -> Void)) {
if let url = URL(string: SignUpAPI) {
let session = URLSession.shared
let bodyData = ["school": "1",
"email": email,
"password": password]
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.httpBody = try! JSONSerialization.data(withJSONObject: bodyData)
let task = session.dataTask(with: request) { (data, response, error) in
if error == nil {
let decoder = JSONDecoder()
if let safeData = data {
do {
let results = try decoder.decode(AccountResults.self, from: safeData)
DispatchQueue.main.async {
self.signUpResponse = results
completion(nil, results)
}
} catch {
print(error)
completion(error, nil)
}
}
}
}
task.resume()
}
}
}
use escaping in your function, I think will get exactly the point server response data or get errors too.
my english is so bad.

Related

SwiftUI Login Issue

I am making an app where I am using API to create login interface.
In my LoginViewModel class I have following login function
import Foundation
class LoginViewModel: ObservableObject {
#Published var loginuser : Login?
// func login(username: String, password: String, callback : #escaping (Bool,LoginData,String) -> Void) {
func login(with params: [String: Any], completionHandler: #escaping (Bool,LoginData,String) -> Void) {
// let parameters: [String: Any] = [
// "email": username,
// "password": password
// ]
var semaphore = DispatchSemaphore (value: 0)
guard let url = URL(string: "https://xxxxxxxxx/v1//user/login")else {return}
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
//request.addValue("token", forHTTPHeaderField: "Authorization")
do {
request.httpBody = try JSONSerialization.data(withJSONObject: params)
} catch let error {
print(error.localizedDescription)
}
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data else {
print(String(describing: error))
semaphore.signal()
return
}
print(String(data: data, encoding: .utf8)!)
}//urlsession
task.resume()
}//login func
}
And in my view I have button whose action has following code
Button(action: {
let params = ["email": userName,
"password": password]
viewModel.login(with: params) { success, data, message in
if success==true {
UserDefaultsStore.isUserLoggedIn = true
// UserDefaultsStore.loginuser = login
showsAlert4 = true
print ("cat1")
}
else
{
print ("cat2")
}
}
}, label: {
Image("btn_arrow")
While I can confirm the API is being read fine as console puts out data from this line in func login
print(String(data: data, encoding: .utf8)!)
What I can not get to work is show "cat1" or "cat2" message in case of successful or unsuccessful login attempt. In fact this piece of code just never executes
if success==true {
UserDefaultsStore.isUserLoggedIn = true
// UserDefaultsStore.loginuser = login
showsAlert4 = true
print ("cat1")
}
else
{
print ("cat2")
}
Any idea where I am going wrong in this? Any help will be appreciated. Thanks
I have tried changing completionHandler: to callback: in func login but that changes nothing.
As someone in the comments mentioned, you are not calling your completionHandler at all. You could also drop the semaphore as it is not needed. Or maybe I am missing the point of the semaphore and you can elaborate on that.
import Foundation
class LoginViewModel: ObservableObject {
#Published var loginuser : Login?
func login(with params: [String: Any], completionHandler: #escaping (Bool,LoginData,String) -> Void) {
var semaphore = DispatchSemaphore (value: 0)
guard let url = URL(string: "https://xxxxxxxxx/v1//user/login")else {return}
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
do {
request.httpBody = try JSONSerialization.data(withJSONObject: params)
} catch let error {
print(error.localizedDescription)
}
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data else {
print(String(describing: error))
semaphore.signal()
completionHandler(false, nil, "Error") -> ON FAILURE
return
}
print(String(data: data, encoding: .utf8)!)
completionHandler(true, data, "") -> ON SUCCESS
}
task.resume()
}

Store JSON data as a variable

I'm trying to figure out how to store JSON data into a variable for later use. How do I store it, and is it possible to use the variable in another view controller, or do I have to do another request to fetch the data?
This is my code:
#IBAction func signinTapped(_ sender: UIButton) {
guard let url = URL(string: "http://XXXXXX/TestReqIOS.php") else {
return
}
let email = txtEmail.text!
let password = txtPassword.text!
let data : Data = "loginSubmit=1&email=\(email)&password=\(password)&grant_type=password".data(using: .utf8)!
var request : URLRequest = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField:"Content-Type");
request.setValue(NSLocalizedString("lang", comment: ""), forHTTPHeaderField:"Accept-Language");
request.httpBody = data
print("Calling API")
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)
// vs let session = URLSession.shared
// make the request
let task = session.dataTask(with: request, completionHandler: {
(data, response, error) in
if let error = error {
print("error")
}
else if let response = response {
print("response")
}
else if let data = data {
print(data)
}
DispatchQueue.main.async { // Correct
guard let responseData = data else {
print("Error: did not receive data")
return
}
print(String(data: responseData, encoding: String.Encoding.utf8) ?? "")
}
})
task.resume()
}
Which will return:
{
"id": "7",
"first_name": "John",
"last_name": "Doe",
"email": "JohnDoe#text.com",
"created": "2019-03-11",
"modified": "2019-03-10",
}
It would be better to use a struct, such as in your case:
struct Data: Codable {
let id: Int
let first_name: String
let last_name: String
let email: String
let created: Date
let modified: Date
}
Then you create a variable of that struct where you will store it:
var dataVariable = [Data]()
Then you can do your URL call like:
func getData(arr: Bool, completion: #escaping (Bool) -> ()) {
let urlJSON = "URL"
guard let url = URL(string: urlJSON) else { return }
URLSession.shared.dataTask(with: url) { (data, response, err) in
guard let data = data else { return }
do {
let getData = try JSONDecoder().decode([Data].self, from: data)
self.dataVariable = getData
} catch let jsonErr {
print("error serializing json: \(jsonErr)")
}
completion(arr)
}.resume()
}
Then you can access all of this from the dataVariable var. IF you do this in a Manager class you can access it from any ViewController.
To access:
let firstNameString = dataVariable[0].first_name
If there are not multiple trees of the same, then just make sure its:
let getData = try JSONDecoder().decode(Data.self, from: data)
Edit:
In your case put the above here:
let task = session.dataTask(with: request, completionHandler: {
(data, response, error) in
if let error = error {
print("error")
}
else if let response = response {
print("response")
}
else if let data = data {
let getData = try JSONDecoder().decode([Data].self, from: data)
self.dataVariable = getData // <- Just decode here
print(data)
}
DispatchQueue.main.async { // Correct
guard let responseData = data else {
print("Error: did not receive data")
return
}
print(String(data: responseData, encoding: String.Encoding.utf8) ?? "")
}
})
task.resume()

Swift 4 send POST request as x-www-form-urlencoded

I want to send a POST request to my php 7 server which accepts data as application/x-www-form-urlencoded. The data I have is inside a Struct and I want to get every property of this struct as a parameter when I submit it.
This is the struct which handles my urlSession requests both GET and POST
XHR.swift
struct XHR {
enum Result<T> {
case success(T)
case failure(Error)
}
func urlSession<T>(method: String? = nil, file: String, data: Data? = nil, completionHandler: #escaping (Result<T>) -> Void) where T: Codable {
let file = file.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed)!
// Set up the URL request
guard let url = URL.init(string: file) else {
print("Error: cannot create URL")
return
}
var urlRequest = URLRequest(url: url)
if method == "POST" {
urlRequest.httpMethod = "POST";
urlRequest.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
urlRequest.httpBody = data
print(urlRequest.httpBody)
}
// set up the session
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)
// vs let session = URLSession.shared
// make the request
let task = session.dataTask(with: urlRequest, completionHandler: {
(data, response, error) in
DispatchQueue.main.async { // Correct
guard let responseData = data else {
print("Error: did not receive data")
return
}
let decoder = JSONDecoder()
print(String(data: responseData, encoding: .utf8))
do {
let todo = try decoder.decode(T.self, from: responseData)
completionHandler(.success(todo))
} catch {
print("error trying to convert data to JSON")
//print(error)
completionHandler(.failure(error))
}
}
})
task.resume()
}
}
This is the functions which sends a POST request to the server:
VideoViewModel.swift
struct User: Codable {
let username: String
let password: String
static func archive(w:User) -> Data {
var fw = w
return Data(bytes: &fw, count: MemoryLayout<User>.stride)
}
static func unarchive(d:Data) -> User {
guard d.count == MemoryLayout<User>.stride else {
fatalError("BOOM!")
}
var w:User?
d.withUnsafeBytes({(bytes: UnsafePointer<User>)->Void in
w = UnsafePointer<User>(bytes).pointee
})
return w!
}
}
enum Login {
case success(User)
case failure(Error)
}
func login(username: String, password: String, completionHandler: #escaping (Login) -> Void) {
let thing = User(username: username, password: password)
let dataThing = User.archive(w: thing)
xhr.urlSession(method: "POST", file: "https://kida.al/login_register/", data: dataThing) { (result: XHR.Result<User>) in
switch result {
case .failure(let error):
completionHandler(.failure(error))
case .success(let user):
//let convertedThing = User.unarchive(d: user)
completionHandler(.success(user))
}
}
}
And I call it like this:
videoViewModel.login(username: "rexhin", password: "bonbon") { (result: VideoViewModel.Login) in
switch result {
case .failure(let error):
print("error")
case .success(let user):
print(user)
}
}
From PHP I can see that a POST request is submitted successfully but when I try to get the username field by doing $_POST["username"] I get Undefined index:
Full code of the app can be seen here https://gitlab.com/rexhin/ios-kida.git
I used below code in swift 4
guard let url = URL(string: "http://192.168.88.129:81/authenticate") else {
return
}
let user1 = username.text!
let pass = passwordfield.text!
print(user1)
print(pass)
let data : Data = "username=\(user1)&password=\(pass)&grant_type=password".data(using: .utf8)!
var request : URLRequest = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField:"Content-Type");
request.setValue(NSLocalizedString("lang", comment: ""), forHTTPHeaderField:"Accept-Language");
request.httpBody = data
print("one called")
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config)
// vs let session = URLSession.shared
// make the request
let task = session.dataTask(with: request, completionHandler: {
(data, response, error) in
if let error = error
{
print(error)
}
else if let response = response {
print("her in resposne")
}else if let data = data
{
print("here in data")
print(data)
}
DispatchQueue.main.async { // Correct
guard let responseData = data else {
print("Error: did not receive data")
return
}
let decoder = JSONDecoder()
print(String(data: responseData, encoding: .utf8))
do {
// let todo = try decoder.decode(T.self, from: responseData)
// NSAssertionHandler(.success(todo))
} catch {
print("error trying to convert data to JSON")
//print(error)
// NSAssertionHandler(.failure(error))
}
}
})
task.resume()
}
You are passing the result of User.archive(w: thing) as the data embedded in the request body, which may never work. Generally, your archive(w:) and unarchive(d:) would never generate any useful results and you should better remove them immediately.
If you want to pass parameters where x-www-form-urlencoded is needed, you need to create a URL-query-like string.
Try something like this:
func login(username: String, password: String, completionHandler: #escaping (Login) -> Void) {
let dataThing = "username=\(username)&password=\(password)".data(using: .utf8)
xhr.urlSession(method: "POST", file: "https://kida.al/login_register/", data: dataThing) { (result: XHR.Result<User>) in
//...
}
}
The example above is a little bit too simplified, that you may need to escape username and/or password before embedding it in a string, when they can contain some special characters. You can find many articles on the web about it.
Another way of doing this is as follows:
Add the URLEncodedFormEncoder.swift into your project. This is a custom URLEncodedFormEncoder from Alamofire / Vapor.
Conform your model to native Swift Encodable protocol, just as you do with JSON coding.
Encode the model just as you do during json encoding
// example
let requstModel = OpenIDCTokenRequest(
clientId: clientId,
clientSecret: clientSecret,
username: username,
password: password
)
guard let requestData: Data = try? URLEncodedFormEncoder().encode(requstModel) else {
return // handle encoding error
}
Quoting from this post
In PHP, a variable or array element which has never been set is
different from one whose value is null; attempting to access such an
unset value is a runtime error.
The Undefined index error occurs when you try to access an unset variable or an array element. You should use function isset inorder to safely access the username param from the POST body. Try the below code in your PHP file.
if (isset($_POST["username"]))
{
$user= $_POST["username"];
echo 'Your Username is ' . $user;
}
else
{
$user = null;
echo "No user name found";
}

Xcode: URL Shared Session not running when unit testing

I have made a simple app which adds data to a database, and then retrieves it. Whilst creating unit testing, it appears that the URLSession.Shared.dataTask is not running. I can see this through the output of the print statements I have setup. Below is my code:
func addChild(childName:String,dob:String,number1:String,number2:String,parentNum:String,parentPass:String,notes:String){
//url to php file
let url = NSURL(string:"http://localhost/addChild.php")
//request to this file
let request = NSMutableURLRequest(url: url as! URL)
//method to pass data to this file
request.httpMethod = "POST"
//body to be appended to url
let body = "childName=\(childName)&dateOfBirth=\(dob)&contact1=\(number1)&contact2=\(number2)&parentAccNum=\(parentNum)&parentAccPass=\(parentPass)&notes=\(notes)"
request.httpBody = body.data(using: String.Encoding.utf8)
print("a")
//launching the request
URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data:Data?, response:URLResponse?, error:Error?) in
print("b")
if (error == nil){
print("c")
//send request
//get main queue in code process to communicate back to user interface
DispatchQueue.main.async(execute: {
do{
//get json result
let json = try JSONSerialization.jsonObject(with: data!,options: JSONSerialization.ReadingOptions.mutableContainers) as? NSDictionary
print("d")
//assigning json to parseJSON in guard/secure way
//checking whether the parsing has worked
guard let parseJSON = json else{
print("Error while parsing")
return
}
//get id from parseJSON dictionary
let id = parseJSON["id"]
//if there is some id value
if id != nil{
print(parseJSON)
self.success = true
print("success")
}
}
catch{
print("Caught an error:\(error)")
}
} )
}
//if unable to proceed request
else{
print("Error:\(error)")
}
//launch prepared session
}).resume()
}
And then below is my unit testing script:
import XCTest
#testable import computerScienceCoursework
class addChildTest: XCTestCase {
//Setting up the values of the text fields
var testChildName:String = "Test name"
var testDOB:String = "99/99/99"
var testContact1:String = "00000000000"
var testContact2:String = "11111111111"
var testParAccNum:String = "-1"
var testParAccPass:String = "Password"
var testNotes:String = "Insert notes here"
var newChild = AddChildController()
override func setUp() {
super.setUp()
// Put setup code here. This method is called before the invocation of each test method in the class.
}
override func tearDown() {
// Put teardown code here. This method is called after the invocation of each test method in the class.
super.tearDown()
}
func testAddChildIsWorking(){
//Assigning the values to the text fields
newChild.addChild(childName: testChildName,dob: testDOB,number1: testContact1,number2: testContact2,parentNum: testParAccNum,parentPass: testParAccPass,notes: testNotes)
XCTAssert(newChild.success == true)
}
}
Problem here is that you donĀ“t know when the async task is finished and the success property is getting updated.
There are some possible solutions for your problem one of them is to add a completion handler to your method.
func addChild(childName:String,dob:String,number1:String,number2:String,parentNum:String,parentPass:String,notes:String, completion: (Bool) -> Void){
//url to php file
let url = NSURL(string:"http://localhost/addChild.php")
//request to this file
let request = NSMutableURLRequest(url: url as! URL)
//method to pass data to this file
request.httpMethod = "POST"
//body to be appended to url
let body = "childName=\(childName)&dateOfBirth=\(dob)&contact1=\(number1)&contact2=\(number2)&parentAccNum=\(parentNum)&parentAccPass=\(parentPass)&notes=\(notes)"
request.httpBody = body.data(using: String.Encoding.utf8)
print("a")
//launching the request
URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data:Data?, response:URLResponse?, error:Error?) in
print("b")
if (error == nil){
print("c")
//send request
//get main queue in code process to communicate back to user interface
DispatchQueue.main.async(execute: {
do{
//get json result
let json = try JSONSerialization.jsonObject(with: data!,options: JSONSerialization.ReadingOptions.mutableContainers) as? NSDictionary
print("d")
//assigning json to parseJSON in guard/secure way
//checking whether the parsing has worked
guard let parseJSON = json else{
print("Error while parsing")
completion(false)
return
}
//get id from parseJSON dictionary
let id = parseJSON["id"]
//if there is some id value
if id != nil{
print(parseJSON)
self.success = true
print("success")
completion(true)
}
}
catch{
print("Caught an error:\(error)")
completion(false)
}
} )
}
//if unable to proceed request
else{
print("Error:\(error)")
completion(false)
}
//launch prepared session
}).resume()
}
Then in your test method you can the method.
func testAddChildIsWorking()
{
let asyncExpectation = expectationWithDescription("addChildIsWorkingFunction")
newChild.addChild(childName: testChildName, dob: testDOB, number1: testContact1,
number2: testContact2, parentNum: testParAccNum, parentPass: testParAccPass, notes: testNotes) { (success) in
asyncExpectation.fulfill()
}
self.waitForExpectationsWithTimeout(10) { error in
XCTAssert(newChild.success == true)
}
}
waitForExpectationWithTimeout is waiting until a fulfill is trigger or a timeout occurs. In this way you could test your async code.
For more informations check this link
Hope that helps.

Synchronous API request to Asynchronous API request Swift 2.2

Well I am new to Swift and I don't know much of completion handler. I want to get a request from an API and parse the JSON response so I can get the token. But what's happening with my code is that whenever I call the getAuthentication function my UI freezes and waiting for the data to get. Here is the code for getAuthentication
func getAuthentication(username: String, password: String){
let semaphore = dispatch_semaphore_create(0);
let baseURL = "Some URL here"
let url = NSURL(string: baseURL)!
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.HTTPBody = "{\n \"username\": \"\(username)\",\n \"password\": \"\(password)\"\n}".dataUsingEncoding(NSUTF8StringEncoding);
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
if error == nil{
let swiftyJSON = JSON(data: data!)
print(swiftyJSON)
//parse the data to get the user
self.id = swiftyJSON["id"].intValue
self.token = swiftyJSON["meta"]["token"].stringValue
} else {
print("There was an error")
}
dispatch_semaphore_signal(semaphore);
}
task.resume()
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
}
then, I am calling this method in my LoginViewController. Someone says that I am using a Synchronous request thats why my UI freezes, but I have really no idea on how to change it to Async and wait for the data to be downloaded. Can someone help me with this? Any help will much be appreciated.
Firstly, remove dispatch_semaphore related code from your function.
func getAuthentication(username: String, password: String){
let baseURL = "Some URL here"
let url = NSURL(string: baseURL)!
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.HTTPBody = "{\n \"username\": \"\(username)\",\n \"password\": \"\(password)\"\n}".dataUsingEncoding(NSUTF8StringEncoding);
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
if error == nil{
let swiftyJSON = JSON(data: data!)
print(swiftyJSON)
//parse the data to get the user
self.id = swiftyJSON["id"].intValue
self.token = swiftyJSON["meta"]["token"].stringValue
} else {
print("There was an error")
}
}
task.resume()
}
In the above code, the function dataTaskWithRequest itself is an asynchronus function. So, you don't need to call the function getAuthentication in a background thread.
For adding the completion handler,
func getAuthentication(username: String, password: String, completion:((sucess: Bool) -> Void)){
let baseURL = "Some URL here"
let url = NSURL(string: baseURL)!
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.HTTPBody = "{\n \"username\": \"\(username)\",\n \"password\": \"\(password)\"\n}".dataUsingEncoding(NSUTF8StringEncoding);
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
var successVal: Bool = true
if error == nil{
let swiftyJSON = JSON(data: data!)
print(swiftyJSON)
self.id = swiftyJSON["id"].intValue
self.token = swiftyJSON["meta"]["token"].stringValue
} else {
print("There was an error")
successVal = false
}
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(successVal)
})
}
task.resume()
}
It can be called as follows:
self.getAuthentication("user", password: "password", completion: {(success) -> Void in
})
You may pass an escaping closure argument to getAuthentication method.
func getAuthentication(username: String, password: String, completion: (JSON) -> ()){
...
// create a request in the same way
...
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
if error == nil{
let swiftyJSON = JSON(data: data!)
print(swiftyJSON)
completion(swiftyJSON)
} else {
print("There was an error")
}
}
task.resume()
}
And call getAuthentication in LoginViewController like this:
getAuthentication(username, password) { (json) -> in
//Do whatever you want with the json result
dispatch_async(dispatch_get_main_queue()) {
// Do UI updates
}
}
Another way to go is calling getAuthentication in a background thread in your LoginViewController to avoid blocking the main thread (i.e. UI thread).
//In LoginViewController
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
getAuthentication(username, password)
dispatch_async(dispatch_get_main_queue()) {
// UI updates
}
}

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