I'm using the SODA Client for swift (Created by Socrata), I just updated to XCode 7 and swift 2 and found some troubles. The one I haven't been able to solve is the completion handler case when it finds an error, it's not accepting the line "syncCompletion(.Error (reqError))" that supposedly should get the error and return to main thread.
I've seen many errors with the same description here "Type of expression is ambiguous without more context", but not in completion handlers, I saw one using do - catch that is different. I'm don't know enough of swift to find out the way to change this.
Some answers suppose you should rewrite the code because some types could have change in swift 2, but I wouldn't know where to start rewriting.
Thanks in advance for your help.
var task = session.dataTaskWithRequest(request, completionHandler: { data, response, reqError in
// We sync the callback with the main thread to make UI programming easier
let syncCompletion = { res in NSOperationQueue.mainQueue().addOperationWithBlock { completionHandler (res) } }
// Give up if there was a net error
if reqError != nil {
syncCompletion(.Error (reqError))
return
}
// Try to parse the JSON
// println(NSString (data: data, encoding: NSUTF8StringEncoding))
var jsonError: NSError?
var jsonResult: AnyObject!
do {
jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers)
} catch var error as NSError {
jsonError = error
jsonResult = nil
} catch {
fatalError()
}
if let error = jsonError {
syncCompletion(.Error (error))
return
}
// Interpret the JSON
if let a = jsonResult as? [[String: AnyObject]] {
syncCompletion(.Dataset (a))
}
else if let d = jsonResult as? [String: AnyObject] {
if let e : AnyObject = d["error"] {
if let m : AnyObject = d["message"] {
syncCompletion(.Error (NSError(domain: "SODA", code: 0, userInfo: ["Error": m])))
return
}
}
syncCompletion(.Dataset ([d]))
}
else {
syncCompletion(.Error (NSError(domain: "SODA", code: 0, userInfo: nil)))
}
})
Solved, I replaced:
if reqError != nil
With
if let error = reqError
and:
syncCompletion(.Error (reqError))
with
syncCompletion(.Error (error))
Related
This question already has answers here:
Swift: Extra argument 'error' in call
(3 answers)
Closed 5 years ago.
I have been trying to login for a while using php but I have a final bug that stops me from finishing. It turns out to give a bug in NSJSONSerialization where the error tells me: error extra argument in call. Then I will provide a screenshot so that the error is clearer and the code so you can help me since I am in a blocking moment and I do not know how to solve it. Thanks in advance
Photo error: [
Code:
#IBAction func loginButtonTapped(sender: AnyObject) {
let userEmail = userEmailTextField.text;
let userPassword = userPasswordTextField.text;
if(userEmail!.isEmpty || userPassword!.isEmpty) { return; }
let myUrl = NSURL(string: "http://localhost/billapp/userSignIn.php");
let request = NSMutableURLRequest(URL:myUrl!);
request.HTTPMethod = "POST";
let postString = "userEmail=\(userEmail)&userPassword=\(userPassword)";
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding);
let task = NSURLSession.sharedSession().dataTaskWithRequest(request){
data, response, error in
if error != nil{
print("error=\(error)")
return
}
var err: NSError?
var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error:NSError) as? NSDictionary
if let parseJSON = json {
var resultValue:String = parseJSON["status"] as String!;
print("result: \(resultValue)")
if(resultValue=="Success")
{
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "isUserLoggedIn");
NSUserDefaults.standardUserDefaults().synchronize();
self.dismissViewControllerAnimated(true, completion: nil);
}
}
}
task.resume()
}
last error
You can follow the quick fix sugestions. Doing so will let you end up like this:
do {
var json = try JSONSerialization.jsonObject(with: Data(), options: .mutableContainers)
if let parseJSON = json {
//your code
}
} catch {
//handle error
}
Unlike Objective C, as per the new methodolgy in Swift, errors are handled using try/catch block instead of passing the error object in the method.
Use the following code for Swift 3.
do {
var json = try JSONSerialization.jsonObject(with: data, options: .mutableContainers)
if let parseJSON = json {
var resultValue:String = parseJSON["status"] as String!;
print("result: \(resultValue)")
if(resultValue=="Success")
{
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "isUserLoggedIn");
NSUserDefaults.standardUserDefaults().synchronize();
self.dismissViewControllerAnimated(true, completion: nil);
}
}
} catch let error {
//Perform the error handling here
}
Following for Swift 2
do {
var json = try NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers)
if let parseJSON = json {
var resultValue:String = parseJSON["status"] as String!;
print("result: \(resultValue)")
if(resultValue=="Success")
{
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "isUserLoggedIn");
NSUserDefaults.standardUserDefaults().synchronize();
self.dismissViewControllerAnimated(true, completion: nil);
}
}
} catch let error {
//Perform the error handling here
}
I am currently trying to download, parse and print JSON from an URL.
So far I got to this point:
1) A class (JSONImport.swift), which handles my import:
var data = NSMutableData();
let url = NSURL(string:"http://headers.jsontest.com");
var session = NSURLSession.sharedSession();
var jsonError:NSError?;
var response : NSURLResponse?;
func startConnection(){
let task:NSURLSessionDataTask = session.dataTaskWithURL(url!, completionHandler:apiHandler)
task.resume();
self.apiHandler(data,response: response,error: jsonError);
}
func apiHandler(data:NSData?, response:NSURLResponse?, error:NSError?)
{
do{
let jsonData : NSDictionary = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary;
print(jsonData);
}
catch{
print("API error: \(error)");
}
}
My problem is, that the data in
do{
let jsonData : NSDictionary = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary;
print(jsonData);
}
remains empty.
When I debug,the connection starts successfully, with the given url as a parameter. But my jsonData variable doesn't get printed. Instead the catch block throws the error, stating that there is no data in my variable:
API error: Error Domain=NSCocoaErrorDomain Code=3840 "No value."
Can someone please help me with this?
What am I missing?
Thank you all very much in advance!
[Edited after switching from NSURL Connection to NSURLSession]
Here's an example on how to use NSURLSession with a very convenient "completion handler".
This function contains the network call and has the "completion handler" (a callback for when the data will be available):
func getDataFrom(urlString: String, completion: (data: NSData)->()) {
if let url = NSURL(string: urlString) {
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url) { (data, response, error) in
// print(response)
if let data = data {
completion(data: data)
} else {
print(error?.localizedDescription)
}
}
task.resume()
} else {
// URL is invalid
}
}
You can use it like this, inside a new function, with a "trailing closure":
func apiManager() {
getDataFrom("http://headers.jsontest.com") { (data) in
do {
let json = try NSJSONSerialization.JSONObjectWithData(data, options: [])
if let jsonDict = json as? NSDictionary {
print(jsonDict)
} else {
// JSON data wasn't a dictionary
}
}
catch let error as NSError {
print("API error: \(error.debugDescription)")
}
}
}
I am getting this error This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes.This will cause an exception in a future release. I don't know what is causing this error. Can anybody help me.
func getUserDataFromTwitterWithUser(user : PFUser)
{
//NRLoader.showLoader()
let strTwURL = "https://api.twitter.com/1.1/users/show.json? screen_name="+PFTwitterUtils.twitter()!.screenName! + "&access_token="+PFTwitterUtils.twitter()!.authToken!
let twURL = NSURL (string: strTwURL)
let request = NSMutableURLRequest(URL: twURL!, cachePolicy: NSURLRequestCachePolicy.UseProtocolCachePolicy, timeoutInterval: 2.0) as NSMutableURLRequest
PFTwitterUtils.twitter()?.signRequest(request)
let session = NSURLSession.sharedSession()
session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in
if error == nil {
var jsonOptional = Dictionary<String, AnyObject>()
do {
jsonOptional = try NSJSONSerialization.JSONObjectWithData(data!, options:NSJSONReadingOptions.MutableContainers ) as! Dictionary<String, AnyObject>
// use jsonData
} catch {
// report error
}
var userName = ""
if let screenName = jsonOptional["screen_name"] as? String{
userName = screenName
}
else if let name = jsonOptional["name"] as? String{
userName = name
}
var profilePicUrl = ""
if let picUrl = jsonOptional["profile_image_url"] as? String{
profilePicUrl = picUrl
}
AppUser.currentUser()?.username = userName
AppUser.currentUser()?.profileAwsURL = profilePicUrl
//NRLoader.hideLoader()
//if ParseUtils.isLoggedInUserIsAnonymous() {
let signUpVC:SignMeUpViewController = self.storyboard!.instantiateViewControllerWithIdentifier("SignMeUpViewController") as! SignMeUpViewController
signUpVC.isFromLogin = true
self.navigationController!.pushViewController(signUpVC, animated: true)
//} else {
// self.pushToSubmitDreamViewController()
//}
}
else {
//NRLoader.hideLoader()
NRToast.showToastWithMessage(error!.description)
}
}).resume()
}
The dataTaskWithRequest call runs in the background and then calls your completion handler from the same thread. Anything that updates the UI should run on the main thread, so all of your current handler code should be within a dispatch_async back onto the main queue:
dispatch_async(dispatch_get_main_queue()) {
// Do stuff to UI
}
Swift 3:
DispatchQueue.main.async() {
// Do stuff to UI
}
Therefore, ideally all the code you currently have within if error == nil should be off in another function, say called handleRequest, so your current code becomes:
session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in
if error == nil {
dispatch_async(dispatch_get_main_queue(), {
self.handleRequest(...)I
})
}
Swift 3
session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in
if error == nil {
DispatchQueue.main.async {
self.handleRequest(...)I
}
}
Should try Symbolic Breakpoint to detect the issue:-
Then put your UI Update code in main thread
DispatchQueue.main.async {}
You'd better change UI only in the main thread
swift3,
let liveInfoUrl = URL(string: "http://192.168.1.66/api/cloud/app/liveInfo/7777")
let task = URLSession.shared.dataTask(with: liveInfoUrl! as URL) {data, response, error in
guard let data = data, error == nil else { return }
DispatchQueue.main.async {
print(String(data: data, encoding: String.Encoding(rawValue: String.Encoding.utf8.rawValue)) ?? "aaaa")
//do some ui work
}
}
if the above suggestions still give you no joy then the sure-est way is to redesign your functions so that getting what you need with
URLSession.shared.dataTask
then hands over so a variable declared outside that function, then a separate UIControl ( button, swipe etc ) displays it to a label or textview or whatever.
After all that is what the error message is telling you. they're separate concerns
I have a function, shown below, that I would like to continuously update. It is taking data from a webpage, and every so often that webpage is updated to reflect current information. Is there a way that I can catch this update and reflect that in my application? I'm pretty new to Swift and iOS programming. Some of the code made seem very bizarre, but it currently works for whatever song is playing when you first open the app (that is, it updates the text to show that song playing but doesn't update later).
let url = NSURL(string: "http://api.vicradio.org/songs/current")!
let request = NSMutableURLRequest(URL: url)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(request) { (data: NSData?, response: NSURLResponse?, error: NSError?) in
if error != nil {
return
}
let name = NSString(data: data!, encoding: NSUTF8StringEncoding) as! String
var songName = ""
var artistName = "by "
var quoteNumber = 0
for character in name.characters {
if character == "\"" {
quoteNumber++
}
if quoteNumber == 3 && character != "\"" {
songName += String(character)
} else if quoteNumber == 7 && character != "\"" {
artistName += String(character)
}
}
if (songName != "no song metadata provided") {
self.SongNowText.text = songName
self.ArtistNowText.text = artistName
self.SongNowText.setNeedsDisplay()
self.ArtistNowText.setNeedsDisplay()
} else if (songName == "no song metadata provided") {
self.SongNowText.text = "The Best of What's Next!"
self.ArtistNowText.text = "only on VIC Radio"
}
}
task!.resume()
It looks like the URL you're accessing there is an API endpoint putting out JSON. I highly recommend using NSJSONSerialization.JSONObjectWithData to parse the response body into a dictionary and use that instead of rolling your own solution by counting quote marks.
The callback to dataTaskWithURL is executed on a background thread. Avoid updating the UI on anything besides the main thread because it can cause problems. Use dispatch_async to execute your UI update function on the main thread as in the example.
All you can do with this API is send it requests and read the responses. You can poll the endpoint at a regular interval while the app is open and get decent results from that. NSTimer is one way to do that, and it requires you put the method you want to execute repeatedly in a class inheriting from NSObject because it depends on Objective-C style message sending.
Throw this in a playground and try it:
import Cocoa
import XCPlayground
XCPSetExecutionShouldContinueIndefinitely()
class RadioDataAccessor : NSObject {
private let callback: [String : AnyObject] -> Void
init(callback: [String : AnyObject] -> Void) {
self.callback = callback
super.init()
NSTimer.scheduledTimerWithTimeInterval(5.0, target: self,
selector: "updateData", userInfo: nil, repeats: true)
// just so it happens quickly the first time
updateData()
}
func updateData() {
let session = NSURLSession.sharedSession()
let url = NSURL(string: "http://api.vicradio.org/songs/current")!
session.dataTaskWithURL(url) { data, response, error in
if error != nil {
return
}
var jsonError = NSErrorPointer()
let json = NSJSONSerialization.JSONObjectWithData(data,
options: NSJSONReadingOptions.allZeros,
error: jsonError) as? [String : AnyObject]
if jsonError != nil {
return
}
dispatch_async(dispatch_get_main_queue()) { self.callback(json!) }
}.resume()
}
}
RadioDataAccessor() { data in
println(data)
}
You may want to save the timer to a variable and expose a function that lets you invalidate it.
Im having an issue, I am trying to create a method which accepts a PFObject as a parameter. The PFObject in this case is the facebook picture URL. The method takes the URL and basically converts it into an image. I can get it to work if i just use this block of code without trying to make it into a method, however I would like to create a method out of this so that I dont have to keep repeating myself. When i try to return the users image i keep getting the error cannot convert the expressions type UIImage to type void swift
Here is the code
func downloadFBUserImage(object: PFObject?) -> UIImage? {
var userProfilePhotoURLString = object?.valueForKey("pictureURL") as String?
if userProfilePhotoURLString != nil {
var pictureURL: NSURL = NSURL(string: userProfilePhotoURLString!)!
var urlRequest: NSURLRequest = NSURLRequest(URL: pictureURL)
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue.mainQueue(), completionHandler: { (NSURLResponse response, NSData data, NSError error) -> Void in
if error == nil && data != nil {
var userProfilePic: UIImage? = UIImage(data: data)
return userProfilePic
}
})
return nil
}
The error is reporting that the completionHandler of the sendAsynchronousRequest is defined to pass you the response, data, and error objects, but that it expects that completionHandler, itself, to not return any values. But you're trying to return a value from within that completionHandler closure.
Bottom line, you cannot simply return the UIImage from your function, because you are performing asynchronous method (i.e. the data is returned later even though you return from the function immediately). So, employ asynchronous pattern:
func downloadFBUserImage(object: PFObject?, completionHandler: (UIImage?, NSError?) -> Void) {
if let userProfilePhotoURLString = object?.valueForKey("pictureURL") as? String {
let pictureURL = NSURL(string: userProfilePhotoURLString)!
let urlRequest = NSURLRequest(URL: pictureURL)
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue.mainQueue()) { (response, data, error) -> Void in
if data != nil {
var userProfilePic = UIImage(data: data)
completionHandler(userProfilePic, nil)
} else {
completionHandler(nil, error)
}
}
}
}
And you'd call it using the same completion handler pattern that sendAsynchronousRequest does:
downloadFBUserImage(object) { image, error in
if image == nil {
println(error)
} else {
// use the image here
}
}
// but don't try to use asynchronously retrieved image here
You cannot return to the completion block like that. The completion block does not have a return parameter. This is why you are getting an error.
For updating the image after download, you can pass in a block along with your downloadFBUserImage function like below.
I used dispatch_async because UI updates have to be done on the main thread.
func downloadFBUserImage(object: PFObject?, completion completionBlock:(UIImage) -> ()) -> (){
var userProfilePhotoURLString = object?.valueForKey("pictureURL") as String?
if userProfilePhotoURLString != nil {
var pictureURL: NSURL = NSURL(string: userProfilePhotoURLString!)!
var urlRequest: NSURLRequest = NSURLRequest(URL: pictureURL)
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue.mainQueue(), completionHandler: { (NSURLResponse response, NSData data, NSError error) -> Void in
if error == nil && data != nil {
if let userProfilePic = UIImage(data: data) {
completionBlock(userProfilePic)
}
}
})
}
}
It can be called like this
func do() {
downloadFBUserImage(pfObject, completion: { (image) -> () in
//updateImage
dispatch_async(dispatch_get_main_queue(), { () -> Void in
// UI updates
}
})
}