Code
let url = NSURL(string:"http://www.stackoverflow.com")
let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { (data, response, error ) in
if error == nil {
var urlContent = NSString(data: data, encoding: NSUTF8StringEncoding)
println(urlContent)
}
}
Try like this:
let url = NSURL(string:"http://www.stackoverflow.com")!
let task = NSURLSession.sharedSession().dataTaskWithURL(url) { (data, response, error) -> Void in
dispatch_async(dispatch_get_main_queue()) {
if let data = data {
if let urlContent = NSString(data: data, encoding: NSUTF8StringEncoding) {
println(urlContent)
}
} else if let error = error {
println(error.description)
}
}
//
}
task.resume()
See the Apple docs for dataTaskWithURL(_:completionHandler:).
After you create the task, you must start it by calling its resume method.
Related
func getResponse(serverName: String) -> String {
var serverResponse: String = "No Response"
let serverURL = "http://" + serverName + ":3000"
if let url = URL(string: serverURL) {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
serverResponse = jsonString
print(jsonString)
}
}
}.resume()
}
return serverResponse
}
I'm trying to set the serverResponse variable from within the if let jsonString but it always returns "No response"(the vars default) and the print function from within the if let jsonString will print out the server response.
DataTask is asynchronous. your function is returning the value before the server request has been completed. You should use a completion handler here.
func getResponse(serverName: String , completion : #escaping (Bool,String?) -> ()) {
let serverURL = "http://" + serverName + ":3000"
if let url = URL(string: serverURL) {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
print(jsonString)
completion(true,jsonString)
}
} else {
completion(false,nil)
}
}.resume()
}
}
Then you can call the above function like this:
getResponse(serverName: "yourServerName") { (isSuccess, response) in
if isSuccess {
self.serverResponse = response ?? ""
} else {
// your api request failed. show alert or whatever you want to inform the user.
}
}
You need to add a completionHandler.
func getResponse(serverName: String, onCompletion: #escaping (String?) -> Void) {
var serverResponse: String = "No Response"
let serverURL = "http://" + serverName + ":3000"
if let url = URL(string: serverURL) {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
serverResponse = jsonString
print(jsonString)
onCompletion(serverResponse)
}
}
}.resume()
}
}
Create serverResponse outside the getResponse(serverName:) method and use property observer didSet to observe the changes in serverResponse, i.e.
var serverResponse: String = "No Response" {
didSet {
print("newValue: ", serverResponse)
//add the code here..
}
}
didSet will be called every time there is any change in serverResponse. So, any code that you want to run after getting the serverResponse from API, write here.
Also, no need to return anything from getResponse(serverName:) method. So, the method will now look like,
func getResponse(serverName: String) {
let serverURL = "http://" + serverName + ":3000"
if let url = URL(string: serverURL) {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
serverResponse = jsonString
print(jsonString)
}
}
}.resume()
}
}
I am trying to build a user regeistration form, which should check if the user already exists. So I am sending a php request to my my mysql server. If the return value is empty, the user does not exists yet.
Unfortunatley I am really stuck with waiting for this check to finish. I tried several solutions I found googleing but none of them worked. My current code uses semaphores and will crash with "fatal error: unexpectedly found nil while unwrapping an Optional value", so the semaphore is not waiting until the task is finished as I would expect it.
Any hints, would be greatly appreciated. Thanks guys.
private func isUniqueEmail(email: String) -> Bool {
var result: Bool?
let semaphore = DispatchSemaphore(value: 1)
let requestURL = URL(string: "http://localhost/firstpostget/functions/get.php")
var request = URLRequest(url: requestURL!)
request.httpMethod = "POST"
let postParameters = "email=" + email
request.httpBody = postParameters.data(using: .utf8)
let configuration = URLSessionConfiguration.default
let session = URLSession(configuration: configuration, delegate: nil, delegateQueue: OperationQueue.main)
let task = session.dataTask(with: request) {(data, response, error) in
var myJson: AnyObject
do{
myJson = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
if myJson.count == 0{
result = true
semaphore.signal()
} else{
result = false
semaphore.signal()
}
} catch{
//TODO
print(error)
}
}
task.resume()
semaphore.wait(timeout: .distantFuture)
return result!
}
Your task is async and you are force unwrapping nil value so this is the reason it crashes.
You have to change your function implementation to also be async, for example using closures:
private func isUniqueEmail(email: String, completion: ((Bool) -> (Void))?) {
let requestURL = URL(string: "http://localhost/firstpostget/functions/get.php")
var request = URLRequest(url: requestURL!)
request.httpMethod = "POST"
let postParameters = "email=" + email
request.httpBody = postParameters.data(using: .utf8)
let configuration = URLSessionConfiguration.default
let session = URLSession(configuration: configuration, delegate: nil, delegateQueue: OperationQueue.main)
let task = session.dataTask(with: request) {(data, response, error) in
var myJson: AnyObject
do{
myJson = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
if myJson.count == 0 {
completion?(true)
} else{
completion?(false)
}
} catch{
//TODO
print(error)
}
}
task.resume()
}
Now you can use this function in this way:
isUniqueEmail(email: "aaa#bbbb.com") { result in
if result {
print("email unique")
} else {
print("email not unique")
}
}
I think you should rethink the pattern you're using to get the data out of your request, you should consider using a custom handler/callback method that you pass along with the email you're trying to check. See below for an example:
private func isUniqueEmail(email: String, handler: ((_ result: Bool) -> Void)?) -> Void {
let requestURL = URL(string: "http://localhost/firstpostget/functions/get.php")
var request = URLRequest(url: requestURL!)
request.httpMethod = "POST"
let postParameters = "email=" + email
request.httpBody = postParameters.data(using: .utf8)
let configuration = URLSessionConfiguration.default
let session = URLSession(configuration: configuration, delegate: nil, delegateQueue: OperationQueue.main)
let task = session.dataTask(with: request) {(data, response, error) in
var myJson: AnyObject
var result: Bool = false
do{
myJson = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as AnyObject
if myJson.count == 0 {
result = true
}
guard handler != nil else {
return
}
handler!(result)
} catch{
//TODO
print(error)
}
}
task.resume()
}
Run:
isUniqueEmail(email: "test#test.com", handler: { result in
print(result) // true || false
})
If you really want to go down the "wait" route then take a took at DispatchGroup's
https://developer.apple.com/documentation/dispatch/dispatchgroup
try using this:
ApihelperClass
static let sharedInstance = ApihelperClass()
typealias CompletionHandler = (_ success:Bool, _ error:Bool, _ result:NSDictionary) -> Void
typealias ErrorHandler = (_ success: Bool, _ error:Bool) -> Void
func callPostRequest(_ urlPath: String, params:[String: AnyObject], completionHandler: #escaping CompletionHandler, errorHandler:#escaping ErrorHandler ){
print("urlPath:==> \(urlPath) ")
let session = Foundation.URLSession.shared
let url = URL(string: urlPath)
var request = URLRequest(url : url!)
request.httpMethod = "POST"
do {
let jsonData = try JSONSerialization.data(withJSONObject: params, options: .prettyPrinted)
request.setValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type")
request.httpBody = jsonData
session.dataTask(with: request, completionHandler: { data, response, error in
OperationQueue.main.addOperation {
guard error == nil && data != nil else { // check for fundamental networking error
print("error=\(error)")
errorHandler(false, true)
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 = \(response)")
}
let responseString = String(data: data!, encoding: String.Encoding.utf8)
print("responseString = \(responseString!)")
if let responsedata = responseString!.data(using: String.Encoding.utf8)! as? Data{
do {
let jsonResult:NSDictionary = try JSONSerialization.jsonObject(with: responsedata, options: []) as! NSDictionary
print("Get The Result \(jsonResult)")
//parse your jsonResult as per your requirements
if error != nil {
print("error=\(error)")
completionHandler(false, true, jsonResult)//
}
if let str = jsonResult["success"] as? NSNull {
print("error=\(str)")
completionHandler(false, true, jsonResult)
}
else {
let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
// print("Response string : \(responseString)")
completionHandler(true, false, jsonResult)
}
} catch let error as NSError {
print(error.localizedDescription)
}
}
}
}) .resume()
}catch {
print("Error ->Catch")
}
}
Add to your viewcontroller
func isUniqueEmail(email: String){
ApihelperClass.sharedInstance.callPostRequest("http://localhost/firstpostget/functions/get.php", params: ["email":email as AnyObject], completionHandler: { (success, error, result) in
//success 200
}) { (success, error) in
//error
}
}
you can use URlSession like :
func isUniqueEmail(email: String,completion: #escaping (Bool) -> ()) {
var request = URLRequest(url: URL(string: "http://localhost/firstpostget/functions/get.php")!)
request.httpMethod = "POST"
let postString = "email=\(email)"
request.httpBody = postString.data(using: .utf8)
// loading to wait request
UIApplication.shared.isNetworkActivityIndicatorVisible = true
let task = URLSession.shared.dataTask(with: request) { data, response, error in
// we get request request
UIApplication.shared.isNetworkActivityIndicatorVisible = false
guard let data = data, error == nil else { // check for fundamental networking error
print("error=\(String(describing: error))")
completion(false)
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))")
completion(false)
}else{
completion(true)
}
let responseString = String(data: data, encoding: .utf8)
print("responseString = \(String(describing: responseString))")
}
task.resume()
}
and used in code Like
self.isUniqueEmail(email: "your Email") { (isExit) in
if isExit {
}else{
}
}
Ok, I just found a solution. My semaphore approach actually worked as well as dispatchgroups. The task just needed to be URLSession.shared.dataTask
Still thank's a lot for all the answers.
#IBAction func mainButtonnBeTapped(sender: AnyObject) {
let session = NSURLSession.sharedSession()
let request = NSURLRequest(URL: NSURL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) -> Void in
let myString = NSString(data: data, encoding: NSUTF8StringEncoding)
println("this is my string: \(myString)")
})
task.resume()
}
I am using above url to try to get some data, but the return is nil, but i enter the url in chrome/safari, i can get some data.
I really don't why, can anyone help to explain?
This HTTP server sends a
Content-Type = application/x-javascript; charset=GBK
header field in the response, therefore you get the correct encoding from the textEncodingName property of the NSURLResponse. This can be
converted to a NSStringEncoding.
This is just a translation of the solution presented in https://stackoverflow.com/a/19885463/1187415 to Swift, plus some
simple error checking:
let session = NSURLSession.sharedSession()
let request = NSURLRequest(URL: NSURL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) -> Void in
var usedEncoding = NSUTF8StringEncoding // Some fallback value
if let encodingName = response.textEncodingName {
let encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding(encodingName))
if encoding != UInt(kCFStringEncodingInvalidId) {
usedEncoding = encoding
}
}
if let myString = NSString(data: data, encoding: usedEncoding) {
println("this is my string: \(myString)")
} else {
println("failed to decode data")
}
})
task.resume()
Output:
this is my string: var hq_str_sz000609="绵世股份, ....
Minor changes are necessary for Swift 2:
let session = NSURLSession.sharedSession()
let request = NSURLRequest(URL: NSURL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) -> Void in
var usedEncoding = NSUTF8StringEncoding // Some fallback value
if let encodingName = response?.textEncodingName {
let encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding(encodingName))
if encoding != UInt(kCFStringEncodingInvalidId) {
usedEncoding = encoding
}
}
if let myString = String(data: data!, encoding: usedEncoding) {
print("this is my string: \(myString)")
} else {
print("failed to decode data")
}
})
task.resume()
Update for Swift 3:
let session = URLSession.shared
let request = URLRequest(url: URL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTask(with: request, completionHandler: {
(data, response, error) -> Void in
guard let data = data else { return }
var usedEncoding = String.Encoding.utf8 // Some fallback value
if let encodingName = response?.textEncodingName {
let encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding(encodingName as CFString))
if encoding != UInt(kCFStringEncodingInvalidId) {
usedEncoding = String.Encoding(rawValue: encoding)
}
}
if let myString = String(data: data, encoding: usedEncoding) {
print("this is my string: \(myString)")
} else {
print("failed to decode data")
}
})
task.resume()
The text you try to get is probably not UTF-8, try with another encoding, like this for example:
let myString = NSString(data: data, encoding: NSASCIIStringEncoding)
Update: read Martin R's answer for how to find the right encoding.
I want to wait for a responseString to complete before calling the next function "nextScreen()" (segue). At the moment I have an if statement to make sure it is not nil before proceeding, but sometimes the the next function/segue is called because the responseString is still downloading.
Could you help with a completion block? I have found completion blocks for NSURLSession, but these just wait for the initial HTTP call to complete, not the response string.
func getProfiles(){
func post(completion: (message: String?) -> Void) {
let request = NSMutableURLRequest(URL: NSURL(string: "http://**.**.**.**/EPG/XML/QueryProfile")!)
request.HTTPMethod = "POST"
let postString = "<QueryProfileReq><type>1</type></QueryProfileReq>"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task: Void = NSURLSession.sharedSession().dataTaskWithRequest(request,
completionHandler: {(data: NSData!,
response: NSURLResponse!,
error: NSError!) in
if error != nil {
println("error=\(error)")
let alert = UIAlertView()
alert.delegate = self
alert.title = "Login Error"
alert.message = "\(error)"
alert.addButtonWithTitle("OK")
alert.show()
self.view.endEditing(true)
return
}
if let responseString = NSString(data: data, encoding: NSUTF8StringEncoding) {
if response != nil {
println("got profiles")
self.nextScreen()
}
self.dataVar = data // UPDATES VARIABLE TO SEND
}
}).resume()
}
}
The convenience method of dataTaskWithRequest essentially returns data or error, with usually some response header type information. If you have an error then you won't have data (99% sure about this). I have re formatted your method to help. The NSString Init Convenience method is synchronous so not quite sure by what you mean by waiting to complete instead of http call?
func getStringFromRequest(completionHandler:(success:Bool, data: NSData?) -> Void) {
let request = NSMutableURLRequest(URL: NSURL(string: "http://##.##.##.##/EPG/XML/QueryProfile")!)
request.HTTPMethod = "POST"
let postString = "<QueryProfileReq><type>1</type></QueryProfileReq>"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in
if let unwrappedError = error {
print("error=\(unwrappedError)")
}
else {
if let unwrappedData = data {
completionHandler(success: true, data: unwrappedData)
return
}
}
completionHandler(success: false, data: nil)
}
task?.resume()
}
func performPost() {
getStringFromRequest { (success, data) -> Void in
if (success) {
if let unwrappedData = data {
self.dataVar = unwrappedData
if let responseString = NSString(data: unwrappedData, encoding: NSUTF8StringEncoding) {
self.nextScreen()
}
}
}
else {
print("Failed")
}
}
}
For example, I have the following code:
let task = NSURLSession.sharedSession().dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
var dann = NSString(data: data, encoding: NSUTF8StringEncoding)!
self.str = dann
})
task.resume()
I want to transfer the data to a variable in the class (the str variable in the class). The string self.str = dann does not convey anything. How can I do this?
I'm not sure NSString is the type you want. JSON may be format of the data returned, depending on your URL's functionality. I tried the code provided and got the same issues, but if you treat it as JSON (I used httpbin.org as a dummy URL source) and it worked.
let task = NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: "http://httpbin.org/get")!, completionHandler: { (data, response, error) -> Void in
do{
let str = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.AllowFragments) as! [String:AnyObject]
print(str)
}
catch {
print("json error: \(error)")
}
})
task.resume()
(thanks for suggested edit #sgthad. the edit is not particularly relevant to the question, but still wanted to update the code to be current.)
Update for Swift 3 syntax
let url = URL(string: "http://httpbin.org/get")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let unwrappedData = data else { return }
do {
let str = try JSONSerialization.jsonObject(with: unwrappedData, options: .allowFragments)
print(str)
} catch {
print("json error: \(error)")
}
}
task.resume()
Can you try dispatch_async?
let task = NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: url)!) {(data, response, error) in
dispatch_async(dispatch_get_main_queue(), {
var dann = NSString(data: data, encoding: NSUTF8StringEncoding)!
self.str = dann
})
}
task.resume()
// Swift 3 based for Quick ref.
let task = URLSession.shared.dataTask(with: NSURL(string: "http://httpbin.org/get")! as URL, completionHandler: { (data, response, error) -> Void in
do{
let str = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.allowFragments) as! [String:AnyObject]
print(str)
} catch {
fatalError("json error: \(error)")
}
})
task.resume()