I'm sending some POST request to my sever with swift, the usual:
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
if error != nil {
println("error=\(error)")
return
}
let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)
println(responseString) //this is fast
label.text = "\(responseString)" // this is very slow
}
task.resume()
This works well, I get the data and all. Now there are 2 things that behave very differently and I can't figure out why.
The line: println(responseString) print the data instantly as expected, however, the line label.text = "\(responseString)" takes about 10 seconds to update the label's text.
Any ideas why? has DrawRect got anything to do with this?
Try doing it on the main thread like this:
dispatch_async(dispatch_get_main_queue(), { () -> Void in
label.text = "\(responseString)"
})
Related
I am new to swift and doing a project in swift 4.0 to acquire data form Fitbit API and got a Strange problem, my url task does not send any urlrequest any more but skip all the code until task.resume, and do not give anything back. Can anyone helps me plz. The code is shown below
import UIKit
class FitbitAPI{
static let sharedInstance : FitbitAPI = FitbitAPI()
var parsedJson : [Any]? = nil
func authorize(with token: String){
let accessToken = token
let baseURL = URL(string: "https://api.fitbit.com/1/user/-/activities/steps/date/today/1m.json")
let request = NSMutableURLRequest(url:baseURL!)
let bodydata = "access_token=\(String(describing: accessToken))"
request.httpMethod = "GET"
request.setValue("Bearer \(String(describing: accessToken))", forHTTPHeaderField: "Authorization")
request.httpBody = bodydata.data(using: String.Encoding.utf8)
let task = URLSession.shared.dataTask(with: request as URLRequest, completionHandler: {[weak self] (data, response, error) in
if let error = error {
print(error)
}
if let data = data, error == nil{
do {
self?.parsedJson = (try JSONSerialization.jsonObject(with: data, options: []) as? [Any] )
print(String(describing: self?.parsedJson))
}catch _{
print("Received not-well-formatted JSON")
}
}
if let response = response {
let httpResponse = response as! HTTPURLResponse
print("response code = \(httpResponse.statusCode)")
}
})
task.resume()
}
}
As #Larme implied in his comment, all of that code between the let task = line and the task.resume() line is a callback. Meaning it won't get called until the task completes. Put breakpoints inside of that callback (like on your if let error = error line), and see if they get hit.
ALso, your URL task is a local variable in this method. That means it's entirely possible that its getting released from memory right at the end of this method, before the callback can even be executed. You'll need a reference to the task outside of the method if you want to guarantee that it stays alive in memory long enough to hit the completion callback.
I found this awesome answer to posting data to php
The only problem is, I don't know how to return the data upon completion.
How can I make a completion handler for the following function?
func postToServer(postURL: String, postString: String) {
let request = NSMutableURLRequest(URL: NSURL(string: postURL)!)
request.HTTPMethod = "POST"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request){
data, response, error in
let responseString = String(data: data!, encoding: NSUTF8StringEncoding)
if responseString != nil {
print("responseString = \(responseString!)")
}
}
task.resume()
}
Edit: Maybe I didn't apply it correctly, but the suggested duplicate link did not solve my problem. Could somebody please provide an example of this? I've been stuck on this for like 3 weeks now. I just don't know how to pull the data from task when it's completed. I've been reading up a lot on closures, but I just don't see where or even how these are related. When I try to find functions related to task, it only gives response...and that returns nil if I don't type in sleep(3) after resume.
I've watched a bunch of videos where people have the same code as me and don't use a completion handler and still get data back... what gives?
This works in swift 3
func postToServer(_ completion:#escaping (( _ response: String, _ success: Bool )-> Void), postURL: String, postString: String) {
let request = NSMutableURLRequest(url: NSURL(string: postURL)! as URL)
request.httpMethod = "POST"
request.httpBody = postString.data(using: String.Encoding.utf8)
let task = URLSession.shared.dataTask(with: request as URLRequest){
data, response, error in
let responseString = String(data: data!, encoding: String.Encoding.utf8)
if responseString != nil {
print("responseString = \(responseString!)")
completion(responseString!, true)
}
}
task.resume()
}
}
This question already has answers here:
How can I get the Data from NSURLSession.sharedSession().dataTaskWithRequest
(2 answers)
Closed 6 years ago.
I'm trying to post from swift to php and then return json encoded data back to swift.
However, print(task.response) is nil. My link does what it is supposed to but my app still responds with nil. Any idea why?
let request = NSMutableURLRequest(URL: NSURL(string: "https://www.flashkase.com/API/createAccount.php")!)
request.HTTPMethod = "POST"
let postString = "username=frogg222"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { data, response, error in
guard error == nil && data != nil else { // check for fundamental networking error
print("error=\(error)")
return
}
if let httpStatus = response as? NSHTTPURLResponse where httpStatus.statusCode != 200 { // check for http errors
print("statusCode should be 200, but is \(httpStatus.statusCode)")
print("response = \(response)")
}
let responseString = String(data: data!, encoding: NSUTF8StringEncoding)
print("responseString = \(responseString)")
}
task.resume()
print(task.response)
And my PHP file
<?php
include($_SERVER["DOCUMENT_ROOT"] . "/inc/database.php");
$arr = [];
$arr[] = 'Reporting for duty';
if($_SERVER['REQUEST_METHOD'] == 'POST'){
$arr[] = 'Post received';
$arr[] = $_POST['username'];
}
echo json_encode($arr);
?>
Update: How can I check for data after completion? If I uncomment sleep(3) it will display results...but that's obviously not ideal.
func postToServer(postURL: String, postString: String) {
let request = NSMutableURLRequest(URL: NSURL(string: postURL)!)
request.HTTPMethod = "POST"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request){
data, response, error in
print("\(data), \(response), \(error)")
}
task.resume()
//sleep(3)
}
let sendURL: String = "https://www.flashkase.com/API/createAccount.php"
let sendData: String = "username=frogg222&email=fake123#gmail.com&password=fake1234"
postToServer(sendURL,postString: sendData)
dataTaskWithRequest is an asynchronous operation. Printing the response code immediately after the task starts will obviously print nil, as it hasn't had time to get a value. The completion handler already has a response object you can use, so inside your completion handler, call print(response) to see the properties and try to get a response code.
I have been following this tutorial to learn Swift and I have a few questions on the way they do things.
Specifically here:
let paramString = "data=Hello"
request.HTTPBody = paramString.dataUsingEncoding(NSUTF8StringEncoding)
let task = session.dataTaskWithRequest(request) {
(data, response, error) in
guard let _:NSData = data, let _:NSURLResponse = response where error == nil else {
print("Error")
return
}
let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding)
print(dataString)
}
Why is (data, response, error) in always used in NSURLSessions? What does this line of code mean? Also, why does he have a guard statement underneath?
The whole section of code is here:
func dataRequest() {
let urlToRequest: String = " http://www.kaleidosblog.com/tutorial/nsurlsession_tutorial.php"
let url: NSURL = NSURL(string: urlToRequest)!
let session = NSURLSession.sharedSession()
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let paramString = "data=Hello"
request.HTTPBody = paramString.dataUsingEncoding(NSUTF8StringEncoding)
let task = session.dataTaskWithRequest(request) {
(data, response, error) in
guard let _:NSData = data, let _:NSURLResponse = response where error == nil else {
print("Error")
return
}
let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding)
print(dataString)
}
task.resume()
}
With NSURLSession you make asynchronous calls, meaning that you make / start a network request and your program continues running - it doesn't stop waiting for response. Then, when your response is ready a completion block gets called / executed. So you need a way to access the data that's coming to you with this response. This data is accessible to you with (data, response, error) properties. This are just the names of those properties, so that you know how to use them. You could have different names, but it would be confusing to anyone else.
You use the guard statement because you can't be sure that you actually have the data or the response. It could be nil if an error occurred (timeout, ...). In such case (if there's an error) you just print "Error" to the console and call return, which makes you leave the completion block without executing the lines let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding) and print(dataString). Of course, if you have the data and the response and error == nil you skip the else block of the guard statement and you just execute you last two lines of code in the block.
Why would my code below successfully return with data, with a statusCode of 200 but fail to convert the returned NSData to an NSString?
var session: NSURLSession
func init() {
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
session = NSURLSession(configuration: config)
}
func getStatic(url:NSURL) {
let request = NSMutableURLRequest(URL: url)
let dataTask = session.dataTaskWithRequest(request) {(data, response, error) in
if error != nil {
// handle error
} else {
// data has a length of 2523 - the contents at the url
if let httpRes = response as? NSHTTPURLResponse {
// httpRes is 200
let html = NSString(data:data, encoding:NSUTF8StringEncoding)
// **** html is nil ****
}
}
}
dataTask.resume()
}
The code is indeed correct.
The URL I was trying to load had non-UTF8 characters and so the encoding attempted by NSString(data:data, encoding:NSUTF8StringEncoding) failed.
Removing none UTF8 characters fixed the problem.
Or selecting an appropriate encoding, NSISOLatin1StringEncoding for my content, also worked.
It looks like it should be fine, to me at least. I'm just dabbling in Swift, but I've done my enclosures (not sure if thats the right name) slightly changed like below. Did you try converting data to NSString prior to your if let httpRes = response as? NSHTTPURLResponse line? Maybe the data variable doesn't actually have the html in it. I have code written almost exactly the same with the changes below that I'm able to successfully convert data to a NSString.
let dataTask = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in
if error != nil {
// handle error
} else {
if let httpRes = response as? NSHTTPURLResponse {
let html = NSString(data:data, encoding:NSUTF8StringEncoding)
}
}
})
Hope it somehow helps.