I am upload multiple image to server using convert image to base64 and send image in a API as a parameter. But when we call api again and again then how to stop api calling on button click. I am using below code to call API.
Thanks in advance
let urlPath: String = "URL"
let url: URL = URL(string: urlPath)!
var request1 = URLRequest(url: url)
request1.httpMethod = "POST"
let stringPost="imgSrc=\(image)"
let data = stringPost.data(using: String.Encoding.utf8)
// print("data\(data)")
request1.httpBody=data
request1.timeoutInterval = 60
let _:OperationQueue = OperationQueue()
let task = session.dataTask(with: request1){data, response, err in
do
{
if data != nil
{
print("data\(String(describing: data))")
if let jsonResult = try JSONSerialization.jsonObject(with: data!, options: []) as? NSDictionary
{
DispatchQueue.main.async
{
print("json\(jsonResult)")
}
}
}
catch let error as NSError
{
DispatchQueue.main.async
{
print("error is \(error)")
print("error desc \(error.localizedDescription)")
}
}}
task.resume()
Make the object task as a global variable, then you can cancel it anywhere by:
task.cancel()
Alternatively, if the object session is a URLSession instance, you can cancel it by:
session.invalidateAndCancel()
If you don't want to allow API call again if there is any previous download is on progress, you can do as follows,
Make your task(URLSessionDataTask type) variable as global variable in the class as follows,
let task = URLSessionDataTask()
Then on your button action do as below by checking the task download status,
func uploadButtonPressed() {
if task.state != .running {
// Make your API call here
} else {
// Dont perform API call
}
}
You can make use following states like running which is provide by URLSessionDataTask class and do action accordingly as per your need,
public enum State : Int {
case running
case suspended
case canceling
case completed
}
You can check result of your task. And if everything is alright you can
task.resume()
but if not
task.cancel()
Related
I recently started with iOS development, and I'm currently working on adding new functionality to an existing app. For this feature I need to obtain a JSON file from a web server. However, if the server is unreachable (no internet/server unavailable/etc), a local JSON needs to be used instead.
In my current implementation I tried using a do catch block, but if there's no internet connection, the app just hangs instead of going to the catch block. JSON parsing and local data reading seem to work fine, the problem is likely in the GET method, as I tried to define a callback to return the JSON data as a separate variable, but I'm not sure if that's the correct way.
What is the best way to handle this scenario?
let url = URL(string: "https://jsontestlocation.com") // test JSON
do {
// make a get request, get the result as a callback
let _: () = getRemoteJson(requestUrl: url!, requestType: "GET") {
remoteJson in
performOnMainThread {
self.delegate.value?.didReceiveJson(.success(self.parseJson(jsonData: remoteJson!)!))
}
}
}
catch {
let localFile = readLocalFile(forName: "local_json_file")
let localJson = parseJson(jsonData: localFile!)
if let localJson = localJson {
self.delegate.value?.didReceiveJson(.success(localJson))
}
}
getRemoteJson() implementation:
private func getRemoteJson(requestUrl: URL, requestType: String, completion: #escaping (Data?) -> Void) {
// Method which returns a JSON questionnaire from a remote API
var request = URLRequest(url: requestUrl) // create the request
request.httpMethod = requestType
// make the request
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
// check if there is any error
if let error = error {
print("GET request error: \(error)")
}
// print the HTTP response
if let response = response as? HTTPURLResponse {
print("GET request status code: \(response.statusCode)")
}
guard let data = data else {return} // return nil if no data
completion(data) // return
}
task.resume() // resumes the task, if suspended
}
parseJson() implementation:
private func parseJson(jsonData: Data) -> JsonType? {
// Method definition
do {
let decodedData = try JSONDecoder().decode(JsonType.self, from: jsonData)
return decodedData
} catch {
print(error)
}
return nil
}
If you don't have to use complex logic with reachability, error handling, request retry etc. just return nil in your completion in case of data task, HTTP and No data errors:
func getRemoteJson(requestUrl: URL, requestType: String, completion: #escaping (Data?) -> Void) {
var request = URLRequest(url: requestUrl)
request.httpMethod = requestType
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
// Task error
guard error == nil else {
print("GET request error: \(error!)")
completion(nil)
return
}
// HTTP error
guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
print("GET request failed: \(response!.description)")
completion(nil)
return
}
// No data
guard let data = data else {
completion(nil)
return
}
completion(data)
}
task.resume()
}
let url = URL(string: "https://jsontestlocation.com")!
getRemoteJson(requestUrl: url, requestType: "GET") { remoteJson in
if let json = remoteJson {
print(json)
...
}
else {
print("Request failed")
...
}
}
func NetworkCheck() -> Bool {
var isReachable = false
let reachability = Reachability()
print(reachability.status)
if reachability.isOnline {
isReachable = true
// True, when on wifi or on cellular network.
}
else
{
// "Sorry! Internet Connection appears to be offline
}
return isReachable
}
Call NetworkCheck() before your API request. If It returns false, read your local json file. if true do remote API call.
Incase after remote API call, any failure check with HTTP header response code.
if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 {
}
I think you need to stop the request from hanging when it’s waiting for a response. The app might be running on a poor connection and be able to get some but not all the data in which case you likely want to failover to the local JSON.
I think you can roughly use what you have but add a timeout configuration on the URLSession as described here: https://stackoverflow.com/a/23428960/312910
I am using URLSessionTask to get the source code of url. When the internet is connected, it works well.
However, when the Internet is disconnected, I try building. And in simulator it is blank and the cpu is 0%. What affects is that My Tab Bar Controller is also missing and blank (It is my initial view controller). It seems that this task is under connecting?
I want the data received from dataTask, so I use semaphore to make it synchronous. Otherwise, as dataTask is an asynchronous action, what I
get is an empty string.
How can I fix this problem?
Thanks!
let urlString:String="http://www.career.fudan.edu.cn/jsp/career_talk_list.jsp?count=50&list=true"
let url = URL(string:urlString)
let request = URLRequest(url: url!)
let session = URLSession.shared
let semaphore = DispatchSemaphore(value: 0)
let dataTask = session.dataTask(with: request,
completionHandler: {(data, response, error) -> Void in
if error != nil{
errorString = "Error!"
}else{
htmlStr = String(data: data!, encoding: String.Encoding.utf8)!
//print(htmlStr)
}
semaphore.signal()
}) as URLSessionTask
//start task
dataTask.resume()
_ = semaphore.wait(timeout: DispatchTime.distantFuture)
Update: As #Moritz mentioned, I finally use completion handler (callback).
func getforData(completion: #escaping (String) -> ()) {
if let url = URL(string: "http://XXXXX") {
let request = URLRequest(url: url)
let task = URLSession.shared.dataTask(with: request) {
data, response, error in
if let data = data, let getString = String(data: data, encoding: String.Encoding.utf8), error == nil {
completion(getString)
} else {
print("error=\(error!.localizedDescription)")
}
}
task.resume()
}
}
And in viewdidload
override func viewDidLoad() {
super.viewDidLoad()
getforData { getString in
// and here we get the "returned" value from the asynchronous task
print(getString) //works well
//tableview should work in main thread
DispatchQueue.main.async {
self.newsTableView.dataSource = self
self.newsTableView.delegate = self
self.newsTableView.reloadData()
}
}
I have made a login screen which takes the input and communicates with the REST api to verify the user. If the response is true, I login the user else not.
I have written a method openViewControllerBasedOnIdentifier(id) to switch views.
The REST api returns true and false appropriately. The push controller gets called but view does not change. How if I place only one line in LoginAction method 'self.openViewControllerBasedOnIdentifier("PlayVC")' and remove the rest of the code , it works fine.
Here is my code
#IBAction func LoginAction(_ sender: Any) {
//self.openViewControllerBasedOnIdentifier("PlayVC")
Constants.login_status = false
//created NSURL
let requestURL = NSURL(string: URL_BK)
//creating NSMutableURLRequest
let request = NSMutableURLRequest(url: requestURL! as URL)
//setting the method to post
request.httpMethod = "POST"
let username = phonenumber.text
//creating the post parameter by concatenating the keys and values from text field
let postParameters = "username="+username!+"&password=bk&schoolId=0";
//adding the parameters to request body
request.httpBody = postParameters.data(using: String.Encoding.utf8)
//creating a task to send the post request
let task = URLSession.shared.dataTask(with: request as URLRequest){
data, response, error in
let responseData = String(data: data!, encoding: String.Encoding.utf8)
if error != nil{
print("error is \(error)")
return;
}
//parsing the response
do {
print(“Received data is ---%#",responseData as Any)
let myJSON = try JSONSerialization.jsonObject(with: data! , options: .allowFragments) as? NSDictionary
if let parseJSON = myJSON {
var status : Bool!
status = parseJSON["status"] as! Bool?
//print(status)
if status==false
{
Constants.login_status = false
}
else{
Constants.login_status = true
print("calling PLAYVC")
self.openViewControllerBasedOnIdentifier("PlayVC")
}
}
else{
print("NULL VALUE RECEIVED")
}
} catch {
print(error)
}
}
//executing the task
task.resume()
}
You should open the new view controller on the main thread like this:
DispatchQueue.main.async {
self.openViewControllerBasedOnIdentifier("PlayVC")
}
Your REST API query response is processed in a background thread when you call URLSession.shared.dataTask and so when you call any UI actions, you should wrap the code as above to execute the UI code in the main thread. Then it would work fine :)
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)¬es=\(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 don´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)¬es=\(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.
I'm making an app in iOS and everything is going fairly well but for one bug that I can't fix. When the user starts the app for the first time the app request a json from my server. When the json is read, I show the result in a picker view. The problem is that the pickerview always shows empty until the user touches the screen. I've tried quite a few things but nothing works. In theory it is empty because the json hasn't been read, but this is not the case because in the console I can see that the json is ready.
Here are the relevant pieces of code:
override func viewDidLoad() {
super.viewDidLoad()
warning.isHidden = true
self.codeInput.delegate = self;
DispatchQueue.main.async {
self.readJson()
self.picker.reloadAllComponents()
}
}
And the part where I read the json
func readJson(){
let urlRequest: NSMutableURLRequest = NSMutableURLRequest(url: requestURL)
let session = URLSession.shared
let task = session.dataTask(with: urlRequest as URLRequest, completionHandler: {
(data, response, error) -> Void in
let httpResponse = response as! HTTPURLResponse
let statusCode = httpResponse.statusCode
if (statusCode == 200) {
print("Everyone is fine, file downloaded successfully.")
do{
let json = try JSONSerialization.jsonObject(with: data!, options:.allowFragments) as! [String:AnyObject]
if let events = json["events"] as? [[String: AnyObject]] {
for event in events {
//here I read the json and I save the data in my custom array
}
self.picker.reloadAllComponents()
}
print(self.eventsArray)
}
}catch {
print("Error with Json: \(error)")
}
}
else{
print(statusCode)
}
})
picker.reloadAllComponents()
task.resume()
}
You need to do a couple of things:
You need to move the call to reload the picker view to inside the completion handler for your data task. That closure gets called once the data has been loaded.
However, the completion methods of URLSession tasks get executed on a background thread. Thus you'll need to wrap your call in a GCD call to the main thread. Add this code as the very last line in your completion closure, right before the closing brace:
DispatchQueue.main.async{
picker.reloadAllComponents()
}
(That's Swift 3 syntax.)
EDIT:
The code would look like this:
func readJson(){
let urlRequest: NSMutableURLRequest = NSMutableURLRequest(url: requestURL)
let session = URLSession.shared
let task = session.dataTask(with: urlRequest as URLRequest, completionHandler: {
(data, response, error) -> Void in
let httpResponse = response as! HTTPURLResponse
let statusCode = httpResponse.statusCode
if (statusCode == 200) {
print("Everyone is fine, file downloaded successfully.")
do{
let json = try JSONSerialization.jsonObject(with: data!, options:.allowFragments) as! [String:AnyObject]
if let events = json["events"] as? [[String: AnyObject]] {
for event in events {
//here I read the json and I save the data in my custom array
}
//Delete this call to reloadAllComponents()
//self.picker.reloadAllComponents()
}
print(self.eventsArray)
}
//------------------------------------
//This is where the new code goes
DispatchQueue.main.async{
picker.reloadAllComponents()
}
//------------------------------------
}catch {
print("Error with Json: \(error)")
}
}
else{
print(statusCode)
}
})
//Delete this call to reloadAllComponents()
//picker.reloadAllComponents()
task.resume()
}