I have this simple code:
let task = session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in
print(response)
do {
let JSON = try NSJSONSerialization.JSONObjectWithData(data!, options:.AllowFragments)
// never printed
print(JSON)
guard let JSONDictionary :NSDictionary = (JSON as! NSDictionary) else {
print("Not a Dictionary")
return
}
print("JSONDictionary! \(JSONDictionary)")
}
catch let JSONError as NSError {
print("\(JSONError)")
}
});
//
task.resume()
Well, I can read the response but then I get (lldb) and the app crashes. The line print(JSON) is never printed. I really can't understand what's going on, any tip is appreciated.
Your data is not JSON, it's JSONP (JSON with Padding). (see Wikipedia)
NSJSONSerialization cannot serialize JSONP.
Since try has failed, print(JSON) won't execute, and the code jumps to the catch block.
Related
I'm performing a post request over my rest api that I built in node. Then the data are stored in a mongodb collection.
This is my code that I use to post the request:
// create dataTask using the session object to send data to the server
let task = session.dataTask(with: request) { data, response, error in
if let error = error {
print("Post Request Error: \(error.localizedDescription)")
return
}
// ensure there is valid response code returned from this HTTP response
guard let httpResponse = response as? HTTPURLResponse,
(200...299).contains(httpResponse.statusCode)
else {
print("Invalid Response received from the server")
return
}
// ensure there is data returned
guard let responseData = data else {
print("nil Data received from the server")
return
}
do {
// create json object from data or use JSONDecoder to convert to Model stuct
if let jsonResponse = try JSONSerialization.jsonObject(with: responseData, options: .mutableContainers) as? [String: ErrorHandler] {
print(jsonResponse)
DispatchQueue.main.async {
self?.isLoading = false
self?.signedIn = true
}
} else {
print("data maybe corrupted or in wrong format")
throw URLError(.badServerResponse)
}
} catch let error {
print(error.localizedDescription)
}
}
task.resume()
The problem is that the responseJson is always nil. I tried to perform the same request with postman and I get the response correctly. What is the problem? Also because the data are correctly uploaded everywhere.
This is my postman result of the same post request.
I am obviously missing something very fundamental/naïve/etc., but for the life of me I cannot figure out how to make simple GET requests.
I'm trying to make an HTTP GET request with Swift 5. I've looked at these posts/articles: one, two, but I can't get print() statements to show anything. When I use breakpoints to debug, the entire section within the URLSession.shared.dataTask section is skipped.
I am looking at the following code (from the first link, above):
func HTTP_Request() {
let url = URL(string: "http://www.stackoverflow.com")!
let task = URLSession.shared.dataTask(with: url) {(data: Data?, response: URLResponse?, error: Error?) in
guard let data = data else { return }
print(String(data: data, encoding: .utf8)!)
}
task.resume()
}
HTTP_Request()
I am running this in a MacOS Command Line Project created through XCode.
I would greatly appreciate any help I can get on this, thank you.
Right now, if there is an error, you are going to silently fail. So add some error logging, e.g.,
func httpRequest() {
let url = URL(string: "https://www.stackoverflow.com")! // note, https, not http
let task = URLSession.shared.dataTask(with: url) { data, response, error in
guard
error == nil,
let data = data,
let string = String(data: data, encoding: .utf8)
else {
print(error ?? "Unknown error")
return
}
print(string)
}
task.resume()
}
That should at least give you some indication of the problem.
A few other considerations:
If command line app, you have to recognize that the app may quit before this asynchronous network request finishes. One would generally start up a RunLoop, looping with run(mode:before:) until the network request finishes, as advised in the run documentation.
For example, you might give that routine a completion handler that will be called on the main thread when it is done. Then you can use that:
func httpRequest(completion: #escaping () -> Void) {
let url = URL(string: "https://www.stackoverflow.com")! // note, https, not http
let task = URLSession.shared.dataTask(with: url) { data, response, error in
defer {
DispatchQueue.main.async {
completion()
}
}
guard
error == nil,
let data = data,
let string = String(data: data, encoding: .utf8)
else {
print(error ?? "Unknown error")
return
}
print(string)
}
task.resume()
}
var finished = false
httpRequest {
finished = true
}
while !finished {
RunLoop.current.run(mode: .default, before: .distantFuture)
}
In standard macOS apps, you have to enable outgoing (client) connections in the “App Sandbox” capabilities.
If playground, you have to set needsIndefiniteExecution.
By default, macOS and iOS apps disable http requests unless you enable "Allow Arbitrary Loads” in your Info.plist. That is not applicable to command line apps, but you should be aware of that should you try to do this in standard macOS/iOS apps.
In this case, you should just use https and avoid that consideration altogether.
Make sure the response get print before exiting the process, you could try to append
RunLoop.main.run()
or
sleep(UINT32_MAX)
in the end to make sure the main thread won't exit. If you want to print the response and exit the process immediately, suggest using DispatchSemaphore:
let semphare = DispatchSemaphore(value: 0)
func HTTP_Request() {
let url = URL(string: "http://www.stackoverflow.com")!
let task = URLSession.shared.dataTask(with: url) {(data: Data?, response: URLResponse?, error: Error?) in
guard let data = data else { return }
print(String(data: data, encoding: .utf8)!)
semphare.signal()
}
task.resume()
}
HTTP_Request()
_ = semphare.wait(timeout: .distantFuture)
This works for me many times I suggest you snippet for future uses!
let url = URL(string: "https://google.com")
let task = URLSession.shared.dataTask(with: ((url ?? URL(string: "https://google.com"))!)) { [self] (data, response, error) in
do {
let jsonResponse = try JSONSerialization.jsonObject(with: data!, options: [])
print(jsonResponse)
guard let newValue = jsonResponse as? [String:Any] else {
print("invalid format")
}
}
catch let error {
print("Error: \(error)")
}
task.resume()
}
I am trying to figure out the simplest way to make an HTTP request in Swift 4 from the command line. I have copied this code from the URLSession programming guide, and added a couple print statements. I can't figure out why the .dataTask is not executing.
print("Testing URLSession")
let sessionWithoutADelegate = URLSession(configuration: URLSessionConfiguration.default)
if let url = URL(string: "https://www.example.com/") {
print("Encoded url \(url)")
(sessionWithoutADelegate.dataTask(with: url) { (data, response, error) in
print("Executing dataTask")
if let error = error {
print("Error: \(error)")
} else if let response = response,
let data = data,
let string = String(data: data, encoding: .utf8) {
print("Response: \(response)")
print("DATA:\n\(string)\nEND DATA\n")
}
}).resume()
}
The objective is to retrieve data from a REST api, but I can't even make a simple GET request to work properly...
I finally figured out how to make it work using CFRunLoop:
let runLoop = CFRunLoopGetCurrent()
let task = session.dataTask(with: request) { (data, response, error) in
print("Retrieved data")
CFRunLoopStop(runLoop)
}
task.resume()
CFRunLoopRun()
print("done")
I am trying to use swiftyjson and I am getting an Error:
Call can throw, but it is marked with 'try' and the error is not
handled.
I have validated that my source JSON is good. I've been searching and cannot find a solution to this problem
import Foundation
class lenderDetails
{
func loadLender()
{
let lenders = ""
let url = URL(string: lenders)!
let session = URLSession.shared.dataTask(with: url)
{
(data, response, error) in
guard let data = data else
{
print ("data was nil?")
return
}
let json = JSON(data: data)
print(json)
}
session.resume()
}
}
Thank you for all the help!
The SwiftyJSON initializer throws, the declaration is
public init(data: Data, options opt: JSONSerialization.ReadingOptions = []) throws
You have three options:
Use a do - catch block and handle the error (the recommended one).
do {
let json = try JSON(data: data)
print(json)
} catch {
print(error)
// or display a dialog
}
Ignore the error and optional bind the result (useful if the error does not matter).
if let json = try? JSON(data: data) {
print(json)
}
Force unwrap the result
let json = try! JSON(data: data)
print(json)
Use this option only if it's guaranteed that the attempt will never fail (not in this case!). Try! can be used for example in FileManager if a directory is one of the default directories the framework creates anyway.
For more information please read Swift Language Guide - Error Handling
You should wrap it into a do-catch block. In your case:
do {
let session = URLSession.shared.dataTask(with: url) {
(data, response, error) in
guard let data = data else {
print ("data was nil?")
return
}
let json = JSON(data: data)
print(json)
}
} catch let error as NSError {
// error
}
Probably you need to implement do{} catch{} block. Inside do block you have to call throwable function with try.
I have a very simple http request which will return a JSON data. Here is my code:
let query = NSString(format: "http://glosbe.com/gapi/translate?from=eng&dest=eng&format=json&phrase=test",src, dest, phrase )
let url = NSURL(string: query)
let task = NSURLSession.sharedSession().dataTaskWithURL(url) {(data, response, error) in
if let httpRes = response as? NSHTTPURLResponse {
println("status code=",httpRes.statusCode)
if httpRes.statusCode == 200 {
println(NSString(data: data, encoding: NSUTF8StringEncoding))
// parse data
let phrase = Phrase.parse(data)
println(phrase.description)
}
}
}
task.resume()
Sometimes the completionHandler isn't called at all. I suspect it's the problem of the server. But when I input the same url into my browser and tried a dozens times. There was no problem at all. The data was returned everything when I refresh the browser.
Is there anything wrong in my code? Thanks
The code works OK for me. I suggest you can make this change to your code (an else clause):
if let httpRes = response as? NSHTTPURLResponse {
println("status code=",httpRes.statusCode)
if httpRes.statusCode == 200 {
println(NSString(data: data, encoding: NSUTF8StringEncoding))
// parse data
let phrase = Phrase.parse(data)
println(phrase.description)
}
} else {
println("error \(error)") // print the error!
}
So you will have a better idea if anything goes wrong