For a screen scraping project I'm using NSURLSession in Swift to read an HTML page. But already the start fails because the returned page gives a redirection to a new webpage and my code doesn't follow that. I thought redirection would work by default, if no delegate is set for the session. But neither case does the redirection. Here's my test project:
import Cocoa
#NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, NSURLSessionTaskDelegate {
#IBOutlet weak var window: NSWindow!
func URLSession(session: NSURLSession, task: NSURLSessionTask, willPerformHTTPRedirection response: NSHTTPURLResponse,
newRequest request: NSURLRequest, completionHandler: (NSURLRequest!) -> Void) {
completionHandler(request);
}
func applicationDidFinishLaunching(aNotification: NSNotification) {
var url = NSURL(string: "https://banking.dkb.de");
let defaultConfigObject = NSURLSessionConfiguration.defaultSessionConfiguration();
let session = NSURLSession(configuration: defaultConfigObject, delegate: self, delegateQueue: nil);
let task = session.dataTaskWithURL(url!, completionHandler: { (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void in
let text = NSString(data: data, encoding: NSUTF8StringEncoding);
// text contains here: <head><meta HTTP-EQUIV="REFRESH" content="0; url=/dkb/"></head>
if var document = NSXMLDocument(data: data, options: Int(NSXMLDocumentTidyHTML), error: nil) {
if let forms = document.nodesForXPath("//form[#name='login']", error: nil) where forms.count > 0 {
let form = forms[0] as! NSXMLNode;
}
}
});
task.resume();
}
func applicationWillTerminate(aNotification: NSNotification) {
// Insert code here to tear down your application
}
}
What do I have to do to make redirection work here?
Update:
On further investigation I found out that it must have to do with the result from the server. For instance using https://www.google.com indeed triggers the redirection delegate. However, since any browser can handle also redirection from the bank address, there must be a different approach in place to properly handle that and I'd like to learn how.
NSURLSession supports 302 redirect and https://www.google.com uses it.
On the other hand, https://banking.dkb.de/ uses meta tag as described. It returns 200(OK) as status code so you must handle it reading meta tag.
Related
Wed 5/18 Additional Info added at Step 5
I am able to create a URLSesion, build a request with a file to upload and successfully call it from my app. On my server side, the proper script is called, uploaded file is saved, etc,. However, I am not receiving the HTTP responses, data, etc.
Actually had this working without the delegate, when the HTTP response functions were within the task itself. But am now trying to expand functionality and am missing something while trying implement the delegate.
The trimmed code is below, and it all works, with the exception of setting up UIViewController as the URLSession delegate. Just trying to figure out why my UIViewController is not receiving the HTTP responses.
Below is the code for:
UIViewController
Class which creates the upload session (UploadService)
Extension for
UIViewController which I want to use to process the responses
How the previous task looked, when it worked. Before I tried to implement the delegate.
Used print to confirm that my UIViewConroller is the delegate, yet it still receives no HTTP response, data, or error messages
UIViewController
class UploadInv : UIViewController {
var xFile : XFile?
...create UI....
let uploadService = UploadService()
lazy var uploadSession: URLSession = {
let configuration = URLSessionConfiguration.default
return URLSession(configuration: configuration, delegate: self, delegateQueue: .main)
}()
override func viewWillAppear(_ animated: Bool) {
...
}
override func viewDidLoad() {
super.viewDidLoad()
uploadService.uploadSession = uploadSession
... code the lays out all buttons, labels, etc...
}
#objc func buttonAction(sender: UIButton!) {
guard let theButton = sender else { return}
let myTag = theButton.tag
switch myTag {
//button to start upload
case ButtType.up.rawValue:
uploadService.start(upFile: xFile!, script: "uploadOrig.pl", upLoadInvClass: self)
uploadService.task?.resume()
//button to select file to upload
case ButtType.file.rawValue:
... file xFile with file info
}
}
UploadService
class UploadService {
var uploadSession : URLSession!
var task: URLSessionUploadTask?
func start(upFile: XFile, script: String, upLoadInvClass: UploadInv) {
var request = upFile.makeUrlReq(upFile: upFile, script: script)
task = uploadSession.uploadTask(with: request, from: request.httpBody! )
print("\(uploadSession.delegate)")
task?.resume()
}
}
extension
extension UploadInv: UIDocumentPickerDelegate, URLSessionDelegate {
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
... file xFile info for upload ....
... http request created ....
}
// Below are the three simple functions which I would handle
// responses the server, but these never seem to get called.
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
if let err = error {
print("Error: \(err.localizedDescription)")
}
}
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: (URLSession.ResponseDisposition) -> Void) {
print("didReceive response")
completionHandler(URLSession.ResponseDisposition.allow)
}
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
print("didReceive data")
if let responseText = String(data: data, encoding: .utf8) {
print(responseText)
}
}
}
Pre-Delegate model which worked
class UploadService {
var uploadSession = URLSession.shared
func start(upFile: XFile, script: String, upLoadInvClass: UploadInv) {
var request = upFile.makeUrlReq(upFile: upFile, script: script)
uploadSession.uploadTask(with: request, from: request.httpBody )
{ (data, response, error) in
if let response = response {
upLoadInvClass.upResp(resp: response)
}
if let error = error {
upLoadInvClass.upErr(error: error)
}
if let data = data {
upLoadInvClass.upData(data: data)
}
}.resume()
}
}
Step 5:
task = uploadSession.uploadTask(with: request, from: request.httpBody! )
print("\(uploadSession.delegate)")
task?.resume()
For other newbies also stuck on this, it turns out there's more than one delegate to look at. There are:
URLSessionTaskDelegate, URLSessionDataDelegate, URLSessionDownloadDelegate, and more. So obviously I was using the wrong one, might have been fell trap to "autocomplete." Nevertheless, I have to make sure I read more documentation on the subject.
Thanks to Scott who "passively/aggressively" gave me the answer, here, while still allowing me to "think." I mean that as a compliment. He told me to add the line:
assert(uploadSession.delegate! is URLSessionDataDelegate)
I have an app that needs to download a file which may be rather large (perhaps as large as 20 MB). I've been reading up on URLSession downloadTasks and how they work when the app goes to the background or is terminated by iOS. I'd like for the download to continue and from what I've read, that's possible. I found a blog post here that discusses this topic in some detail.
Based on what I've read, I first created a download manager class that looks like this:
class DownloadManager : NSObject, URLSessionDownloadDelegate, URLSessionTaskDelegate {
static var shared = DownloadManager()
var backgroundSessionCompletionHandler: (() -> Void)?
var session : URLSession {
get {
let config = URLSessionConfiguration.background(withIdentifier: "\(Bundle.main.bundleIdentifier!).background")
return URLSession(configuration: config, delegate: self, delegateQueue: OperationQueue())
}
}
private override init() {
}
func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
DispatchQueue.main.async {
if let completionHandler = self.backgroundSessionCompletionHandler {
self.backgroundSessionCompletionHandler = nil
completionHandler()
}
}
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
if let sessionId = session.configuration.identifier {
log.info("Download task finished for session ID: \(sessionId), task ID: \(downloadTask.taskIdentifier); file was downloaded to \(location)")
do {
// just for testing purposes
try FileManager.default.removeItem(at: location)
print("Deleted downloaded file from \(location)")
} catch {
print(error)
}
}
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
if totalBytesExpectedToWrite > 0 {
let progress = Float(totalBytesWritten) / Float(totalBytesExpectedToWrite)
let progressPercentage = progress * 100
print("Download with task identifier: \(downloadTask.taskIdentifier) is \(progressPercentage)% complete...")
}
}
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
if let error = error {
print("Task failed with error: \(error)")
} else {
print("Task completed successfully.")
}
}
}
I also add this method in my AppDelegate:
func application(_ application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: #escaping () -> Void) {
DownloadManager.shared.backgroundSessionCompletionHandler = completionHandler
// if the app gets terminated, I need to reconstruct the URLSessionConfiguration and the URLSession in order to "re-connect" to the previous URLSession instance and process the completed download tasks
// for now, I'm just putting the app in the background (not terminating it) so I've commented out the lines below
//let config = URLSessionConfiguration.background(withIdentifier: identifier)
//let session = URLSession(configuration: config, delegate: DownloadManager.shared, delegateQueue: OperationQueue.main)
// since my app hasn't been terminated, my existing URLSession should still be around and doesn't need to be re-created
let session = DownloadManager.shared.session
session.getTasksWithCompletionHandler { (dataTasks, uploadTasks, downloadTasks) -> Void in
// downloadTasks = [URLSessionDownloadTask]
print("There are \(downloadTasks.count) download tasks associated with this session.")
for downloadTask in downloadTasks {
print("downloadTask.taskIdentifier = \(downloadTask.taskIdentifier)")
}
}
}
Finally, I start my test download like this:
let session = DownloadManager.shared.session
// this is a 100MB PDF file that I'm using for testing
let testUrl = URL(string: "https://scholar.princeton.edu/sites/default/files/oversize_pdf_test_0.pdf")!
let task = session.downloadTask(with: testUrl)
// I think I'll ultimately need to persist the session ID, task ID and a file path for use in the delegate methods once the download has completed
task.resume()
When I run this code and start my download, I see the delegate methods being called but I also see a message that says:
A background URLSession with identifier com.example.testapp.background already exists!
I think this is happening because of the following call in application:handleEventsForBackgroundURLSession:completionHandler:
let session = DownloadManager.shared.session
The getter for the session property in my DownloadManager class (which I took directly from the blog post cited previously) is always trying to create a new URLSession using the background configuration. As I understand it, if my app had been terminated, then this would be the appropriate behavior to "reconnect" to the original URLSession. But since may app is not being terminated but rather just going to the background, when the call to application:handleEventsForBackgroundURLSession:completionHandler: happens, I should be referencing the existing instance of URLSession. At least I think that's what the problem is. Can anyone clarify this behavior for me? Thanks!
Your problem is that you are creating a new session every time you reference the session variable:
var session : URLSession {
get {
let config = URLSessionConfiguration.background(withIdentifier: "\(Bundle.main.bundleIdentifier!).background")
return URLSession(configuration: config, delegate: self, delegateQueue: OperationQueue())
}
}
Instead, keep the session as an instance variable, and just get it:
class DownloadManager:NSObject {
static var shared = DownloadManager()
var delegate = DownloadManagerSessionDelegate()
var session:URLSession
let config = URLSessionConfiguration.background(withIdentifier: "\(Bundle.main.bundleIdentifier!).background")
override init() {
session = URLSession(configuration: config, delegate: delegate, delegateQueue: OperationQueue())
super.init()
}
}
class DownloadManagerSessionDelegate: NSObject, URLSessionDelegate {
// implement here
}
When I do this in a playground, it shows that repeated calls give the same session, and no error:
The session doesn't live in-process, it's part of the OS. You're incrementing reference count every time you access your session variable as written, which causes the error.
I'm working on programming with Swift for the first time, and in doing so I'm following along with this tutorial. Unfortunately it looks like the tutorial is a little outdated and most of the code is throwing Buildtime errors. The most reoccurring error is the NSURLSession has been renamed to URLSession. I've tried letting Swift fix it, but in many cases it just starts throwing warnings.I'm also getting a Value type HomeModel has no member'parseJSON' error as well as a NSDat is not implicitly convertible to data error. From what I can tell, it looks like the NSURL is no longer used, but I'm not sure about the other two. Seeing how this is the first Swift project I've worked on, I'm not sure how to fix these. Can someone provide some insight on how to fix these mistakes?
here is the code:
import Foundation
protocol HomeModelProtocal: class {
func itemsDownloaded(items: NSArray)
}
class HomeModel: NSObject, NSURLSessionDataDelegate {
//properties
weak var delegate: HomeModelProtocal!
var data : NSMutableData = NSMutableData()
let urlPath: String = "http://testurl.com/service.php" //this will be changed to the path where service.php lives
func downloadItems() {
let url: NSURL = NSURL(string: urlPath)!
var session: NSURLSession!
let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
session = NSURLSession(configuration: configuration, delegate: self, delegateQueue: nil)
let task = session.dataTaskWithURL(url)
task.resume()
}
func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData) {
self.data.appendData(data);
}
func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?) {
if error != nil {
print("Failed to download data")
}else {
print("Data downloaded")
self.parseJSON()
}
}
}
Several basic types have dropped the "NS" prefix in Swift 3.0. Earlier in swift 2.2, we used to have NSUserDefaults, NSURLSession, NSFileManager etc. Now, most of them dropped their prefix "NS" and changed to UserDefaults, URLSession, FileManager etc.
Your code contains a lot of types with 'NS' prefix. By simply removing it, your code can be converted to Swift 3. Your converted code looks like as shown below:
protocol HomeModelProtocal: class {
func itemsDownloaded(items: NSArray)
}
class HomeModel: NSObject, URLSessionDataDelegate {
//properties
weak var delegate: HomeModelProtocal!
var data : Data = Data()
let urlPath: String = "http://testurl.com/service.php" //this will be changed to the path where service.php lives
func downloadItems() {
let url: URL = URL(string: urlPath)!
var session: URLSession!
let configuration = URLSessionConfiguration.default
session = URLSession(configuration: configuration, delegate: self, delegateQueue: nil)
let task = session.dataTask(with: url)
task.resume()
}
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
self.data.append(data);
}
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
if error != nil {
print("Failed to download data")
}else {
print("Data downloaded")
self.parseJSON() // This class doesn't have a function parseJSON(). So, it's giving you an error like this
}
}
}
Also, I don't see any function called parseJSON() in your class. I believe you have to add it.
Most of my programming experience is in Shell and Python. I'm fairly new to Swift, like "3 days ago" new. I just can't figure out why didFinishDownloadtingTo is not called when my downloadTask completes. Here's my AppDelegate.swift file:
import Cocoa
#NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, URLSessionDelegate, URLSessionDownloadDelegate {
#IBOutlet weak var window: NSWindow!
#IBOutlet var progressind: NSProgressIndicator!
#IBOutlet var outputtext: NSTextField!
func applicationDidFinishLaunching(_ aNotification: Notification) {
// Insert code here to initialize your application
let requestURL: URL = URL(string: "https://www.apple.com")!
let urlRequest: URLRequest = URLRequest(url: requestURL as URL)
let session = URLSession.shared
let downloads = session.downloadTask(with: urlRequest)
print("starting download...")
downloads.resume()
}
func applicationWillTerminate(_ aNotification: Notification) {
// Insert code here to tear down your application
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL){
print("download finished!")
}
}
I'm using Swift 3, and I just cannot find enough documentation on it to figure this out on my own.
I went a little crazy declaring classes trying to figure out why it wasn't working right, so I'm sure there are also some errors there.
It appears to download the file successfully. I've tried with several URLs. The "Disk" and "Network" sections of the debug menu appear consistent with downloading a file of the size at every URL I've tested with.
The thing is that when you use NSURLSession(URLSession in Swift 3) you have to choose if you want to use a delegate or a completion handler, in case of use both, only the completion handler gets called. In your case the delegate is not set so you can't see the call to the delegate methods. Instead you should specify the delegate using the another initializer of NSURLSession like in the following code:
#NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, URLSessionDelegate, URLSessionDownloadDelegate {
func applicationDidFinishLaunching(_ aNotification: Notification) {
let requestURL: URL = URL(string: "https://www.apple.com")!
let urlRequest: URLRequest = URLRequest(url: requestURL as URL)
let config = URLSessionConfiguration.default
let session = URLSession(configuration: config, delegate: self, delegateQueue: OperationQueue.main)
let downloads = session.downloadTask(with: urlRequest)
print("starting download...")
downloads.resume()
}
func applicationWillTerminate(_ aNotification: Notification) {
// Insert code here to tear down your application
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL){
print("download finished!")
}
}
And then you should see the delegate method called properly.
I hope this help you
The key lies in the word "delegate". It's like the dog in the night-time in the Sherlock Holmes story. The dog did nothing in the night. The word "delegate" never appears in your code!
But it needs to. didFinishDownloadingTo is a delegate method. You can only receive this method if you are the delegate of the NSURLSession. You need to set self as its delegate. The runtime doesn't magically read your mind and know that you intend this object as the delegate; you have to tell it.
I'm having a problem detecting when data is being received using NSURLSession. The equivalent code with NSURLConnection does work, but that's not included here.
In this example, I'm doing a request to google.com. The completionHandler works and "complete" is printed (also the data, etc if you change the code).
However didReceiveData isn't triggered and "received data" is never printed.
I've been through the docs and done a ton of searching and I think this looks right, but I can't seem to get it to work. Definitely would appreciate any help with this.
(I need to use didReceiveData because I'm going to parsing a streaming json api.)
Thanks!
import UIKit
class ViewController: UIViewController, NSURLSessionDelegate, NSURLSessionDataDelegate, NSURLSessionTaskDelegate {
override func viewDidAppear(animated: Bool) {
let session = NSURLSession.sharedSession()
var task = session.dataTaskWithURL(NSURL(string: "https://google.com")!, completionHandler: { (data, response, error) -> Void in
print("complete")
})
task.resume()
}
func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData) {
print("received data")
}
}
There were two issues.
When the session is created, you must define a delegate. That was the main reason didReceiveData wasn't being called.
The second issue is that if you use a completionHandler block, then all the delegates functions are bypassed. In the code for NSURlSession, it says
extension NSURLSession {
/*
* data task convenience methods. These methods create tasks that
* bypass the normal delegate calls for response and data delivery,
* and provide a simple cancelable asynchronous interface to receiving
* data. Errors will be returned in the NSURLErrorDomain,
* see <Foundation/NSURLError.h>. The delegate, if any, will still be
* called for authentication challenges.
*/
You must implement each delegate function you need to check for completion, errors, etc.
The updated code is below:
import UIKit
class ViewController: UIViewController, NSURLSessionDelegate {
override func viewDidAppear(animated: Bool) {
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession(configuration: config, delegate: self, delegateQueue: nil)
var task = session.dataTaskWithURL(NSURL(string: "https://google.com")!)
task.resume()
}
func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData) {
print("received data")
}
}
You can get data in completionHandler only. Why do you want to use didReceiveData?
Below code will show you how you can get the received data
override func viewDidAppear(animated: Bool) {
let session = NSURLSession.sharedSession()
var task = session.dataTaskWithURL(NSURL(string: "https://google.com")!, completionHandler: { (data, response, error) -> Void in
if NSJSONSerialization.isValidJSONObject(data){
if let jsonParam = try? NSJSONSerialization.dataWithJSONObject(dictData, options: []){
print("Result Data : \(jsonParam)")
}
}
})
task.resume()
}