I have a performance problem implementing a REST client related with long delays. Problem is not present on my Android app or any REST client adding to browsers so it is not related with backend issues.
this is my function for executing API call:
func getRecordsMethod(completion: #escaping ((_ result: Data) -> Void)){
let defaults = UserDefaults.standard
let username = defaults.object(forKey: "username") as! String
let password = defaults.object(forKey: "password") as! String
let loginString = String(format: "%#:%#", username, password).description
let loginData = loginString.data(using: String.Encoding.utf8)
let base64LoginString = loginData?.base64EncodedString()
let url = URL (string: apiURL + getPersonalBests )
var request = URLRequest(url: url!)
request.httpMethod = "GET"
request.setValue("Basic " + base64LoginString!, forHTTPHeaderField: "Authorization")
let task = URLSession.shared.dataTask(with: request) { data, response, error in
if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode == 200 {
completion(data!)
}
}
task.resume()
}
and how I call it in my ViewController :
override func viewDidLoad() {
super.viewDidLoad()
populateRecords()
}
func populateRecords(){
self.records.removeAll()
apiRestManager.getRecordsMethod() {
(result: Data) in
let json = JSON(data: result)
for (_, subJson) in json {
// processing response- adding to personalBestTable
}
DispatchQueue.main.async {
self.personalBestTable.reloadData()
}
}
}
The biggest issue is that after function populateRecords is being started there is delay approx 2-3 seconds after a call is visible on my backend (after that processing and table reload is made instantly)
Can anyone give me a hint how I can optimize requests speed?
Getting the data from UserDefault on main threat may cause the delay.
Change your viewDidLoad method with following code
override func viewDidLoad() {
super.viewDidLoad()
let concurrentQueue = DispatchQueue(label: "apiQueue", attributes: .concurrent)
concurrentQueue.async {
populateRecords()
}
}
Related
I am updating my collectionView with a response from my api using Combine to provide real time info. My api returns NSArray which is working but for some strange reasons inside my SearchAPI class I can receive the response and print it out in the console print("Our array ", searchArray) but can't sink to my UIViewController and update my collectionView accordingly. print("value ", value) Value is always empty
import Foundation
import Combine
class SearchAPI {
static let shared = SearchAPI()
func fetchData(url: String, category: String, queryString: String) -> Future<NSArray, Error>{
var searchArray: NSArray = []
let urlString = url
print("url come ", urlString)
guard let url = URL(string: urlString) else {
fatalError()
}
var request = URLRequest(url: url)
request.setValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request) { [weak self] data, response, error in
guard let data = data, error == nil else {
return
}
do{
let json = try? JSONSerialization.jsonObject(with: data, options: []) as? NSArray
if let responseJson = json {
searchArray = responseJson
print("Our array", searchArray)
}
}
}
task.resume()
return Future { promixe in
DispatchQueue.main.async {
promixe(.success(searchArray))
}
}
}
}
//In my UIViewController
var observers: [AnyCancellable] = []
let action = PassthroughSubject<NSArray, Never>()
var category = "tv"
var queryString = ""
private var models: NSArray = []
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
if isMovieSelected {
btnMoviesBottomBorder.backgroundColor = .secondaryPink
btnAlbumsBottomBorder.backgroundColor = .systemGray
btnAlbumsBottomBorder.backgroundColor = .systemGray
}
txtSearch.searchTextField.addTarget(self, action: #selector(searchItem), for: .editingChanged)
}
#objc func searchItem(){
moviesView.alpha = 0
albumsView.alpha = 0
booksView.alpha = 0
lblSrchResults.alpha = 1
queryString = txtSearch.text!.replacingOccurrences(of: " ", with: "%20")
print("who is calling ", queryString)
let url = "https://endpoint?category=\(category)&query=\(queryString)"
SearchAPI.shared.fetchData(url: url, category: category, queryString: queryString)
.receive(on: DispatchQueue.main)
.sink(receiveCompletion: { completion in
switch completion {
case .finished:
print("finished")
case .failure(let error):
print(error)
}
}, receiveValue: { [weak self] value in
print("value ", value)
self?.models = value
self?.searchCollectionView!.reloadData()
}).store(in: &observers)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
print("Fetched ", models.count)
return models.count
}
In your fetchData function, you create a dataTask to run the URL request. At some point later on that dataTask will complete and return an array.
Then you create a Future and send some code off to run on the main queue. That code has nothing inside of it to make it wait until the dataTask completes.
The code inside the Future is going to run "right away" and complete before a value has been assigned to searchArray.
You need to change your Future so that it only resolves (only completes) after the dataTask is done. Just tweaking your code a bit it looks something like:
func fetchData(url: String, category: String, queryString: String) -> Future<NSArray, Error>
{
return Future { promixe in
var searchArray: NSArray = []
let urlString = url
print("url come ", urlString)
guard let url = URL(string: urlString) else {
fatalError()
}
var request = URLRequest(url: url)
request.setValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data,
error == nil else {
promixe(.failure(error!))
return
}
do{
let json = try? JSONSerialization.jsonObject(with: data, options: []) as? NSArray
if let responseJson = json {
searchArray = responseJson
print("Our array", searchArray)
promixe(.success(searchArray))
}
}
}
task.resume()
}
}
I typed this into a playground, but I did not run it, so additional changes may be necessary.
All of the action now happens inside the future. Once you are in a future block then you should call its resolution function (in your code called promixe) for all success or failure cases.
I changed your code so that promixe is called ONLY when the data task completes (successfully or unsuccessfully).
For your code you should probably also:
Be sure to call proximate, once, on every path through your Futures block. In particular you need to catch the error that JSONSerialization might give you and called promixe to report the error. Otherwise your future may not complete if data comes back from the server, but it cannot be parsed.
Change your code to use Swift style JSON instead of using JSONSerialization that way you will have an [SomeType] instead of NSArray. Use the type system to your advantage to reduce the possibility of errors.
Instead of doing queryString = txtSearch.text!.replacingOccurrences(of: " ", with: "%20") use
txtSearch.text!.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed). It will cover more cases if the user types
something unexpected.
In my iOS App i'm able to download data from a database, but actually all the operations are made in background and the main thread is still active, even the GUI. I also tried to make a 'sleep' with
DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(3)) { ... }
With this delay everthing works fine, but it's not a good solution. How can i change my code to do this in the main thread? Possibly with loadingIndicator.
This is my code (checking if username exists):
func CheckIfUsernameExists(username : String, passwordFromDb : inout String, errorMsg : inout String)
{
//declare parameter as a dictionary which contains string as key and value combination. considering inputs are valid
var _errorMsg = ""
var _psw = ""
var parameters : [String : Any]?
parameters = ["username": username,
"action": "login"]
print(parameters!)
let session = URLSession.shared
let url = "http://www.thetestiosapp.com/LoginFunctions.php"
let request = NSMutableURLRequest()
request.url = URL(string: url)!
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.setValue("application/json", forHTTPHeaderField:"Accept")
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField:"Content-Type")
do{
request.httpBody = try JSONSerialization.data(withJSONObject: parameters!, options: .sortedKeys)
let task = session.dataTask(with: request as URLRequest, completionHandler: {(data, response, error) in
if let response = response {
let nsHTTPResponse = response as! HTTPURLResponse
let statusCode = nsHTTPResponse.statusCode
print ("status code = \(statusCode)")
}
if let error = error {
print ("\(error)")
}
if let data = data {
do{
_psw = self.parseJSON_CheckIfUsernameExists(data, errorMsg: &_errorMsg)
}
}
})
task.resume()
}catch _ {
print ("Oops something happened buddy")
errorMsg = "Usarname non recuperato (1)"
}
passwordFromDb = _psw
errorMsg = _errorMsg
}
You’re attempting to update passwordFromDb and errorMsg at the end of this method. But this is an asynchronous method and and those local variables _psw and _errorMsg are set inside the closure. Rather than trying to defer the checking of those variables some arbitrary three seconds in the future, move whatever “post request” processing you need inside that closure. E.g.
func CheckIfUsernameExists(username : String, passwordFromDb : inout String, errorMsg : inout String) {
//declare parameter as a dictionary which contains string as key and value combination. considering inputs are valid
let parameters = ...
let session = URLSession.shared
var request = URLRequest()
...
do {
request.httpBody = ...
let task = session.dataTask(with: request) { data, response, error in
if let httpResponse = response as? HTTPURLResponse,
let statusCode = httpResponse.statusCode {
print ("status code = \(statusCode)")
}
guard let data = data else {
print (error ?? "Unknown error")
return
}
let password = self.parseJSON_CheckIfUsernameExists(data, errorMsg: &_errorMsg)
DispatchQueue.main.async {
// USE YOUR PASSWORD AND ERROR MESSAGE HERE, E.G.:
self.passwordFromDb = password
self.errorMsg = _errorMsg
// INITIATE WHATEVER UI UPDATE YOU WANT HERE
}
}
task.resume()
} catch _ {
print ("Oops something happened buddy")
errorMsg = "Usarname non recuperato (1)"
}
}
I have this question for Xcode9 Swift 4. I am trying to fetch some data from some api, and I need to use these data to display. However, since the urlSession is highly asynchronous, I cannot get the data at the right time (most of the time the data is nil). Here is the code.
func getUserInfo(){
let data = user!.Data as? [String : Any] ?? nil
if let data = data{
let ID = data["ID"] as? Int ?? nil
if let ID = ID{
let jsonUrlString = "SomeString"
let requestUrl = URL(string: jsonUrlString)
var request = URLRequest(url: requestUrl!)
request.httpMethod = "GET"
request.setValue("SomeKey", forHTTPHeaderField: "AppKey")
request.setValue(md5("Someinfo"), forHTTPHeaderField: "Sign")
dataTask = URLSession.shared.dataTask(with: request){(data, response, err) in
guard let data = data, err == nil else { // check for fundamental networking err
print("error=\(String(describing: err))")
return
}
if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {
// check for http errors
print("statusCode should be 200, but is \(httpStatus.statusCode)")
print("response = \(String(describing: response))")
}
do{
guard let json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [Any] else{return}
var userInfo = userDetail(json: json)
let dataDic = userInfo.dataArray as? [String:Any] ?? nil
userInfo.ID = dataDic?["ID"] as? Int
userInfo.AccountName = dataDic?["AccountName"] as? String
userInfo.Avatar = dataDic?["Avatar"] as? String
} catch let jsonErr{
print(jsonErr)
}
}
dataTask?.resume()
}
}
}
I am storing the data into variable userInfo, which has properties like ID, Account Name, and Avatar. But when I call the function in another method "configNavigationBar", it cannot initialize userInfo for me.
func configNavigationBar(){
getUserInfo()
if dataTask?.state == .completed{
navigationItem.title = userInfo?.AccountName
navigationItem.setHidesBackButton(true, animated: true)
navigationController?.navigationBar.prefersLargeTitles = true
}
}
Can anybody help me with the question! I deeply appreciate any help.
How about changing title after successful http request? In a callback. You can configure everything except title before receiving data.
func configNavigationBar(){
getUserInfo { accountName in
self.navigationItem.title = accountName
}
navigationItem.setHidesBackButton(true, animated: true)
navigationController?.navigationBar.prefersLargeTitles = true
}
func getUserInfo(_ callback: #escaping (String) -> Void) {
...
var userInfo = userDetail(json: json)
let dataDic = userInfo.dataArray as? [String:Any] ?? nil
userInfo.ID = dataDic?["ID"] as? Int
userInfo.AccountName = dataDic?["AccountName"] as? String
userInfo.Avatar = dataDic?["Avatar"] as? String
// here's the insertion
callback(userInfo.AccountName)
// end of insertion
....
}
You might also need to wrap ui update into main thread if http request is using background thread.
getUserInfo { accountName in
DispatchQueue.main.async {
self.navigationItem.title = accountName
}
}
You simply need to wait until your data has been downloaded.
While download is busy you should decide to show temporary state on your navigation bar.
Then, when download is finished (or fails), you update the navigation bar again.
I have a table in a view controller that is populated through a dictionary from which information is retrieved via a JSON request. In the viewDidLoad() function, I call the function that retrieves the data which is added to `IncompletedDeadlines dictionary:
override func viewDidLoad() {
super.viewDidLoad()
self.IncompleteDeadlines = [String:AnyObject]()
self.retrieveIncompletedDeadlines()
}
Everything works however the table only shows when interacted with. I thought maybe the best way to show the table the moment the view appears is by adding a tableView.reload to viewDidAppear as so:
override func viewDidAppear(_ animated: Bool) {
self.tableView.reloadData()
}
But this doesn't fix it. I have attached pictures for clarity of the situation. Picture one shows the view the moment the view appears. Picture 2 only happens once the table is interacted with i.e. swiped. So my question is how can I get the table to show immediately? I understand there can be a delay because of the load, but I shouldn't have to interact with it for it to show:
When the view is interacted with i.e. swiped:
The retrieveIncompletedDeadlines() function is as so:
func retrieveIncompletedDeadlines(){
let myUrl = NSURL(string: "https://www.example.com/scripts/retrieveIncompleteDeadlines.php");
let request = NSMutableURLRequest(url:myUrl! as URL)
let user_id = UserDetails[0]
request.httpMethod = "POST";
let postString = "user_id=\(user_id)";
request.httpBody = postString.data(using: String.Encoding.utf8);
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
if error != nil {
print("error=\(String(describing: error))")
return
}
var err: NSError?
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
if let parseJSON = json {
let checker:String = parseJSON["status"] as! String;
if(checker == "Success"){
let resultValue = parseJSON["deadlines"] as! [String:AnyObject]
self.IncompleteDeadlines = resultValue
}
self.tableView.reloadData()
}
} catch let error as NSError {
err = error
print(err!);
}
}
task.resume();
self.tableView.reloadData()
}
JSON will be parsed on the background thread but any update to the UI must be done on the main thread hence you have to do it inside DispatchQueue.main.async {} This article explains well what is the problem.
Furthermore I would write a completions handler which returns the data once the operation has finished. This is another interesting article about.
Completion handlers are super convenient when your app is doing something that might take a little while, like making an API call, and you need to do something when that task is done, like updating the UI to show the data.
var incompleteDeadlines = [String:AnyObject]()
override func viewDidLoad() {
super.viewDidLoad()
//please note your original function has changed
self.retrieveIncompletedDeadlines { (result, success) in
if success {
// once all the data has been parsed you assigned the result to self.incompleteDeadlines
self.incompleteDeadlines = result
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
}
}
func retrieveIncompletedDeadlines(_ completion:#escaping ([String:AnyObject] , _ success: Bool)-> Void){
let myUrl = NSURL(string: "https://www.example.com/scripts/retrieveIncompleteDeadlines.php");
let request = NSMutableURLRequest(url:myUrl! as URL)
let user_id = UserDetails[0]
request.httpMethod = "POST";
let postString = "user_id=\(user_id)";
request.httpBody = postString.data(using: String.Encoding.utf8);
let task = URLSession.shared.dataTask(with: request as URLRequest) {
data, response, error in
if error != nil {
print("error=\(String(describing: error))")
return
}
var err: NSError?
do {
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
if let parseJSON = json {
let checker:String = parseJSON["status"] as! String;
var resultValue = [String:AnyObject]()
if(checker == "Success"){
resultValue = parseJSON["deadlines"] as! [String:AnyObject]
}
completion(resultValue, true)
}
} catch let error as NSError {
err = error
print(err!);
}
}
task.resume();
}
}
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
}
}