My ViewController is set to update JSON data on a server. That works perfectly. But when I set my VC to perform a segue back to another segue it crashes with the following statement:
fatal error: unexpectedly found nil while unwrapping an Optional value
This happens at this line:
let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as! NSArray
The error happens on the "UpdateVC" and the segue points to "ListVC".
The ending part of that statement is doing a forced unwrapping:
as! NSArray
since it throws an exception, it means that either:
the return value is nil
the return value cannot be cast to NSArray
I can't say what the correct way to handle that would be, because it depends on your app logic. If the cast should (ideally) always succeed, then you probably have a bug in your app. On the other hand, if it's possible that the cast doesn't succeed, then the best way is to protect that with an optional binding:
if let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as? NSArray {
// do something
}
Related
I m using this code to call my rest web service.
But if I try to decode the result of web service call I received error.
class func callPostServiceReturnJson(apiUrl urlString: String, parameters params : [String: AnyObject]?, parentViewController parentVC: UIViewController, successBlock success : #escaping ( _ responseData : AnyObject, _ message: String) -> Void, failureBlock failure: #escaping (_ error: Error) -> Void) {
if Utility.checkNetworkConnectivityWithDisplayAlert(isShowAlert: true) {
var strMainUrl:String! = urlString + "?"
for dicd in params! {
strMainUrl.append("\(dicd.key)=\(dicd.value)&")
}
print("Print Rest API : \(strMainUrl ?? "")")
let manager = Alamofire.SessionManager.default
manager.session.configuration.timeoutIntervalForRequest = 120
manager.request(urlString, method: .get, parameters: params)
.responseJSON {
response in
switch (response.result) {
case .success:
do{
let users = try JSONDecoder().decode(OrderStore.self, from: response.result.value! as! Data)
}catch{
print("errore durante la decodifica dei dati: \(error)")
}
if((response.result.value) != nil) {
success(response as AnyObject, "Successfull")
}
break
case .failure(let error):
print(error)
if error._code == NSURLErrorTimedOut {
//HANDLE TIMEOUT HERE
print(error.localizedDescription)
failure(error)
} else {
print("\n\nAuth request failed with error:\n \(error)")
failure(error)
}
break
}
}
} else {
parentVC.hideProgressBar();
Utility.showAlertMessage(withTitle: EMPTY_STRING, message: NETWORK_ERROR_MSG, delegate: nil, parentViewController: parentVC)
}
}
This is the error that I can print:
Could not cast value of type '__NSDictionaryI' (0x7fff86d70b80) to 'NSData' (0x7fff86d711e8).
2021-09-27 16:34:49.810245+0200 ArrivaArrivaStore[15017:380373] Could not cast value of type '__NSDictionaryI' (0x7fff86d70b80) to 'NSData' (0x7fff86d711e8).
Could not cast value of type '__NSDictionaryI' (0x7fff86d70b80) to 'NSData' (0x7fff86d711e8).
CoreSimulator 732.18.6 - Device: iPhone 8 (6F09ED5B-8607-4E47-8E2E-A89243B9BA90) - Runtime: iOS 14.4 (18D46) - DeviceType: iPhone 8
I generated OrderStore.swift class from https://app.quicktype.io/
//EDIT
.responseJSON returns deserialized JSON, in this case a Dictionary. It cannot be cast to Data what the error clearly confirms.
To get the raw data you have to specify .responseData
Replace
.responseJSON {
response in
switch (response.result) {
case .success:
do {
let users = try JSONDecoder().decode(OrderStore.self, from: response.result.value! as! Data)
with
.responseData {
response in
switch response.result {
case .success(let data):
do {
let users = try JSONDecoder().decode(OrderStore.self, from: data)
Consider that AF 5 supports even .responseDecodable to decode directly into the model
.responseDecodable {
(response : DataResponse<OrderStore,AFError>) in
switch response.result {
case .success(let users): print(users)
Side notes:
As mentioned in your previous question there is no AnyObject in the AF API. The parameters are [String:Any] and responseData is the decoded type. I recommend to make the function generic and use the convenient Result type.
Delete the break statements. This is Swift.
This is an addendum to Vadian's answer. I'm trying to illustrate the process that lead you into this error, with the hopes that you can notice it in the future, before it leads you astray
This is a pretty common "pattern" of error.
Picture it as though you're traversing a maze, starting from some initial data format, and trying to get to some destination data format. At each point along the way, there are several options to choose from, some which get you closer to your goal, and some which lead you further away.
You've chosen to enter the maze at the entryway called responseJSON, whose callback will give you a AFDownloadResponse<Any> (which is the inferred type of the variable you called response).
JSON structures always have an array or dictionary at the top level. Since Alamofire can't statically know which kind of JSON you'll be dealing with, it models this with an Any. At runtime, the type of the Value will be either NSDictionary (or one of its concrete subclasses, like __NSDictionaryI) or NSArray (or one of its concrete subclasses).
You then decide to get the result of that response. Its static type is Result<Any, Error>. You switch over this error, ensuring you're dealing with the success case and not the failure case. Inexplicably, you ignore the payload value associated with the success, but later force unwrap it out with result.response.value!.
result.response.value is an Any, but to placate the compiler your force-cast it to a Data. But we already know this will only ever be an NSArray or NSDictionary, so this will never work.
You could keep wandering around in this area of the maze, and stumble to the end goal via a long path. For example, you could force cast to NSDictionary, then re-serialize that dictionary structure back to a JSON string, which you can turn into Data, only for you to then pass it to JSONDecoder().decode, which will then decode that JSON back. Of course, this is all awfully round-about and wasteful. The issue was the that responseJSON maze entrance was not the right one for where you're trying to go!
You could have instead entered into the responseData maze entrance, which gets you right to your Data destination!
Though you might then realize that the Data was a red herring all along. You didn't actually want Data. You wanted to decode an OrderStore, and Data was how you thought you needed to get there. But it turns out that so many people were entering through the Data entrance with the intent to decode some JSON, that the Alamofire people carved out a new entrance just for you: responseDecodable. It takes you right to the OrderStore, and fiddles around with the JSON, Data or whatever, under the hood where you don't have to worry about it.
Using AlamoFire I can make an API call to my endpoint, it works and connects as expected. Using the print tools I can print the JSON response to the console and see the JSON string, but I am unable to get this string to move to the next function.
I keep getting the error:
"fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)"
My code looks like this:
func getDataForUser(Username:String, UserToken:String) {
print("Getting data for user \(Username)")
Alamofire.request(.POST, baseURL+userdataURL, parameters: ["Username": Username, "UserToken": UserToken]).response { (req, res, data, error) -> Void in
let jSONResponse: NSDictionary = (try! NSJSONSerialization.JSONObjectWithData(data!,options: NSJSONReadingOptions.MutableContainers)) as! NSDictionary
print(jSONResponse)
if(jSONResponse["Success"] as! Bool == true) {
print("Success! API Request Worked")
self.delegate!.didReceiveAPIResults(jSONResponse)
}
}
}
The error is on line:
self.delegate!.didReceiveAPIResults(jSONResponse)
The console looks like this:
jSONResponse NSDictionary 2 key/value pairs 0x78e8d6a0
[0] (null) "Success" : "1"
[1] (null) "Response" : 2 key/value pairs
The debug screen for jSONResponse gives me data that I can drill into so I know its not nil.
Where is the nil coming from and how do I resolve?
In Swift, "1" is not equal to a Bool value of true.
It's crashing at jSONResponse["Success"] as! Bool == true. You could change this to jSONResponse["Success"] as! String == "1".
If you are able to modify the source of the API you're consuming, you're probably better of making Success a true/false JSON bool value, and leaving your Swift code as is.
My initial thoughts were that the JSON handler or API Controller were wrong.
What I had not passed was the delegate variable in the view controller setup.
EG:
api.delegate = self
Thank you to #paulvs and Eric D for pointing that out.
I am coding a hangman game and am loading the possible words into my app using json text files. I tried to follow the examples of others on this website but I am getting errors from Xcode.
I tried the following code based on another answer:
import Foundation
var error: NSError?
let jsonData: NSData = /* get your json data */
let jsonDict = NSJSONSerialization.JSONObjectWithData(jsonData, options: nil, error: &error) as NSDictionary
But I got an errors on line 4 with jsonDict that said "call can throw but is not marked with try, and the error is not handled" and "Type JSONReadingOptions does not conform to protocol NilLiteralConvertible".
Here is the JSON File I would like to parse:
{
“wordList” : {
“difficulty” : “Easy”
“list” : [
“fireplace”,
“apple”,
“january”,
“tooth”,
“cookies”,
“mysterious”,
“essential”,
“magenta",
“darling”,
“pterodactyl”
]}}
I would like to be able to go into my list array and get values. Thank you very much for any help!
In Swift 2 you need to use the new error handling API instead of passing a reference to an NSError:
do {
let jsonDict = try NSJSONSerialization.JSONObjectWithData(jsonData, options: NSJSONReadingOptions(rawValue: 0)) as? NSDictionary
if let jsonDict = jsonDict {
// work with dictionary here
} else {
// more error handling
}
} catch let error as NSError {
// error handling
}
You also can't pass nil as value to the options parameter, you need to pass a value of type NSJSONReadingOptions.
That said, the most common approach for parsing JSON in Swift is currently using third party libraries, such as Argo because they can save you a lot of code that is necessary to validate and safely cast the content of your JSON data to the correct Swift types.
Im trying to parse json in weather app, but have hit a snag that i cannot get past.
I do get an error, "Type 'int' does not conform to Protocol 'StringLiteralConvertible'" in the following code.
Ive tried casting the jsonResult["main"] but that does instead give the error "Operand of postfix should have optional type, type is AnyObject". Do i need to downcast the Array in some way and how, if so, should i do that?
I´ve searched so much for this but could not find any help in other posts. Code as follows.
func updateWeatherInfo(latitude: CLLocationDegrees, longitude: CLLocationDegrees) {
Alamofire.request(.GET, AlongRequest)
.responseJSON { (_, _, JSON, error) in
println(JSON)
self.updateUISuccess(JSON as NSArray!)
}
}
func updateUISuccess(jsonResult: NSArray) {
self.loading.text = nil
self.loadingIndicator.hidden = true
self.loadingIndicator.stopAnimating()
if let tempResult = ((jsonResult["main"] as NSArray)["temp"] as? Double)
This would be easier to give a definitive answer to if you provide the JSON that you're trying to parse, but the error message you're getting is clear.
That error is because you're trying to access what you've declared as an NSArray instance with a string subscript, twice in this one line:
if let tempResult = ((jsonResult["main"] as NSArray)["temp"] as? Double)
jsonResult is declared as an NSArray parameter, and then you're casting jsonResult["main"] to NSArray before trying to subscript it with ["temp"]. The problem here is that NSArray (and built-in Swift arrays) only use integer-based subscripting. The error is saying that where the Swift compiler is expecting an Int, you've provided a string literal.
To fix this, you'll need to go in one of two directions. If the structure you're trying to access actually has these string keys, then you should be using NSDictionary instead of NSArray in both cases. If not, and it's an integer-index array, you should be using integers.
I am new to iOS development. I am using Swift and I have very little experience with Objective-C, so some of the other possibly related answers are tricky to understand. I am trying to understand how to use NSURLSession to get some data from a JSON file on the Web. I found some useful information about getting a file from a URL, but like this other StackOverflow user (NSURLSessionDataTask dataTaskWithURL completion handler not getting called), I heard that NSURLConnection was not the current way to get data, so I'm trying to use NSURLSession.
When I am getting my JSON from the bundle, I am using this extension to
Dictionary (I am pretty sure I got this code from a tutorial):
static func loadJSONFromBundle(filename: String) -> Dictionary<String, AnyObject>? {
let path = NSBundle.mainBundle().pathForResource(filename, ofType: ".json")
if !path {
println("Could not find level file: \(filename)")
return nil
}
var error: NSError?
let data: NSData? = NSData(contentsOfFile: path, options: NSDataReadingOptions(),
error: &error)
if !data {
println("Could not load level file: \(filename), error: \(error!)")
return nil
}
let dictionary: AnyObject! = NSJSONSerialization.JSONObjectWithData(data,
options: NSJSONReadingOptions(), error: &error)
if !dictionary {
println("Level file '\(filename)' is not valid JSON: \(error!)")
return nil
}
return dictionary as? Dictionary<String, AnyObject>
}
I'd like to do something similar for getting a dictionary from a JSON file that is on the web because I don't anticipate wanting to include all of my JSON files in the bundle. So far, I have this:
static func loadJSONFromWeb(urlstring: String) -> Dictionary<String, AnyObject>? {
let url = NSURL(string: urlstring)
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession(configuration: config, delegate: nil, delegateQueue: NSOperationQueue())
var error: NSError?
//I think I am using the completionHandler incorrectly. I'd like to access the data from the download
let task = session.downloadTaskWithRequest(NSURLRequest(URL: url), {(url, response, error) in println("The response is: \(response)")
})
task.resume()
//Isn't this contentsOfURL thing supposed to go with the connection stuff rather than the session stuff?
//How can I do this with a session? How can I create and use a completionHandler? This way seems clunky.
let data: NSData? = NSData(contentsOfURL: url)
if !data {
println("Could not load data from file: \(url), error: \(error!)")
return nil
}
println("The data is: \(data)")
let dictionary: AnyObject! = NSJSONSerialization.JSONObjectWithData(data,
options: NSJSONReadingOptions(), error: &error)
if !dictionary {
println("The file at '\(url)' is not valid JSON, error: \(error!)")
return nil
}
return dictionary as? Dictionary<String, AnyObject>
}
I think that my actual question that most needs answering is this: Where
is the data? I don't think I am using sessions and tasks correctly. I feel like I'm
starting a session to connect to a specific URL and using resume() to
start the download task I want to make happen, but I don't know how to
get the data from that JSON file.
If I need to use a completionHandler and a request in a way similar to what I found here:
(popViewControllerAnimated work slow inside NSURLSessionDataTask) can someone please explain how the 'data' in the completionHandler relates to the data in the fie I am trying to read/download? I am a bit baffled by the completionHandler and how to use it properly.
I looked at the documentation for NSData as well, but I didn't see anything that helped me understand how to get data from my session (or how to initialize an instance of NSData given my session). As far as I can tell form the documentation for NSURLDownloadTask, the task itself is not how I can access the data. It looks like the data comes from the session and task through the completionHandler.
EDIT:
I also looked at the documentation for NSURLSessionDownloadDelegate, but I could really use an example in Swift with some explanation about how to use the delegate. This led me to the URL Loading System Programming Guide. I'm guessing the benefits of using a session must be huge if the documentation is this complicated. I'm going to keep looking for more information on the URL Loading System.
I found this answer helpful (but I'm so new I can't upvote anything yet): https://stackoverflow.com/a/22177659/3842582 It helped me see that I am probably going to need to learn to use a delegate.
I also looked at the URL Loading System Programming Guide. I think what I really need is help with a completionHandler. How can I get my data? Or, am I already doing it correctly using NSData(contentsOfURL: url) (because I don't think I am).
Thank you in advance for any help you can offer!
First, let data: NSData? = NSData(contentsOfURL: url) will return your JSON synchronously. Did you try that and get this working simply? That way you can get started with the rest of your processing while figuring out NSURLSession.
If you're going to use NSURLSession, or a lot of other things in iOS, you need to learn delegates. Fortunately, they're easy. In terms of syntax you just add it to your class declaration like you were inheriting from it. What that does is say that you are going to implement at least the required functions for the delegate. These are callback functions which are generally pretty well documented. It is quite straightforward once you understand it.
If this is not a "heavyweight" project that really needs NSURLSession, you should look at this Swift library. Besides being a really nice way to deal with JSON there is a synchronous call to directly load the JSON from a url. https://github.com/dankogai/swift-json/
Why is NSURLConnection not the correct way to get data? You just should be careful with synchronous requests. Here is an example of how to get data from an url.
func synchronousExampleRequest() -> NSDictionary {
//creating the request
let url: NSURL! = NSURL(string: "http://exampledomain/apiexample.json")
var request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "GET"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
var error: NSError?
var response: NSURLResponse?
let data = NSURLConnection.sendSynchronousRequest(request, returningResponse: &response, error: &error)
error = nil
let resultDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers, error: &error) as! NSDictionary
return resultDictionary
}