I'm trying to get results from an API, and I'm having trouble running the request itself.
Here is the code I currently have:
let url = URL(string: "https://httpbin.org/get")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let error = error {
print("error: \(error)")
} else {
if let response = response as? HTTPURLResponse {
print("statusCode: \(response.statusCode)")
}
if let data = data, let dataString = String(data: data, encoding: .utf8) {
print("data: \(dataString)")
}
}
}
task.resume()
However, it doesn't seem to run anything inside the code block in dataTask.
Thanks for your help :)
Your code works well. It seems like you're just calling the function incorrectly...try it this way:
1:
func request() {
let url = URL(string: "https://httpbin.org/get")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let error = error {
print("error: \(error)")
} else {
if let response = response as? HTTPURLResponse {
print("statusCode: \(response.statusCode)")
}
if let data = data, let dataString = String(data: data, encoding: .utf8) {
print("data: \(dataString)")
}
}
}
task.resume()
}
2:
override func viewDidLoad() {
super.viewDidLoad()
request()
}
Please check if there's something wrong
I have a block of code that use API to get a list of film but nothing happens.
typealias JSONDictHandler = (([String : Any]?) -> Void)
let session = URLSession(configuration: .default)
var request = URLRequest(url: URL(string: "http://dev.bsp.vn:8081/training-movie/movie/list")!)
let token = "dCuW7UQMbdvpcBDfzolAOSGFIcAec11a"
request.httpMethod = "GET"
request.setValue(token, forHTTPHeaderField: "app_token")
let dataTask = session.dataTask(with: request) { (data, response, error) in
// if nothing wrong
if error == nil {
if let httpResponse = response as? HTTPURLResponse {
switch httpResponse.statusCode {
case 200: // successful case
if let data = data {
do {
let jsonDict = try JSONSerialization.jsonObject(with: data, options: .mutableContainers)
print(jsonDict)
} catch let error as NSError {
print("Error: \(error.localizedDescription)")
}
}
default:
print("HTTP Response Code: \(httpResponse.statusCode)")
}
}
// there's something wrong
} else {
print("Error: \(String(describing: error?.localizedDescription))")
}
}
dataTask.resume()
Besides, there're some parameters I have to insert to the url, how can I do this?
Hope this is helpful!!
Allow arbitrary load to yes
This question already has answers here:
function with dataTask returning a value
(4 answers)
Closed 5 years ago.
I try to create function to get data from URL:
func getStringFromUrl(urlString: String) -> String {
if let requestURL = URL(string: urlString) {
let session = URLSession(configuration: URLSessionConfiguration.default)
let task = session.dataTask(with: requestURL, completionHandler: { (data, response, error) in
if let data = data {
do {
let str = String(data: data, encoding: String.Encoding.utf8)
return str
}
catch let error as NSError {
print ("error = \(error)")
}
}
else {
print ("error = \(error)")
}
})
task.resume()
}
}
But I got this error: unexpected non-void return value in void function
How can I create a separate function to get data from Url?
In your code you have:
let str = String(data: data, encoding: String.Encoding.utf8)
return str
Which is inside a closure block which is not defined to return anything. Because the function session.dataTask is an asynchronous task, it won't return straight away. You should use a completion block/closure to get the response when it returns. Also bear in mind that it might not return, so the string needs to be optional. See the code below.
func getStringFromUrl(urlString: String, completion: #escaping (_ str: String?) -> Void) {
if let requestURL = URL(string: urlString) {
let session = URLSession(configuration: URLSessionConfiguration.default)
let task = session.dataTask(with: requestURL, completionHandler: { (data, response, error) in
if let data = data {
do {
let str = String(data: data, encoding: String.Encoding.utf8)
completion(str)
}
catch let error as NSError {
print ("error = \(error)")
completion(nil)
}
}
else {
print ("error = \(error)")
completion(nil)
}
})
task.resume()
}
}
EDIT: Usage
getStringFromUrl(urlString: "http://google.com") { str in
if let text = str {
// you now have string returned
}
}
I have to call a webservice from getResonse(url) then i want to return json . I am unable how to return json in complete handler . They give me error Unexpected non void return value in void function Please help.Any help would be apperciated. Thanks in Advance
func GetStation(url : String) {
var dict = NSDictionary()
dict = getResonse(url)
}
func getResonse(myUrl:NSString) ->NSDictionary
{
let request = NSMutableURLRequest(URL: NSURL(string: myUrl as String)!, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringCacheData, timeoutInterval: 30)
let session = NSURLSession.sharedSession()
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
request.HTTPMethod = "GET"
let task = session.dataTaskWithRequest(request) { data, response, error in
guard data != nil else{
return
}
do {
if let json = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary {
print(json)
if (data == nil)
{
return nil
error
}
else
{
return json
error
}
}else {
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding) // No error thrown, but not NSDictionary
print("Error could not parse JSON: \(jsonStr)")
}
} catch let parseError {
print(parseError) // Log the error thrown by `JSONObjectWithData`
let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
print("Error could not parse JSON: '\(jsonStr)'")
}
}
task.resume()
}
This is merely a coding error (possibly due to braces being all over the place).
In you completion handler, you have 3 forced exits two of which return a value and one that doesn't.
from the "guard data ..." --> else { return }
in the do { ... return nil ... or return json ... }
from the error message I gather that the later two returns are incorrect.
You are inside the dataTaskWithRequest: of NSUrlSession which returns
func dataTaskWithRequest(request: NSURLRequest, completionHandler: (NSData?, NSURLResponse?, NSError?) -> Void) -> NSURLSessionDataTask
It returns Void inside the block. So it's showing an error.
I adapted this from Ray Wenderlich's iOS Apprentice tutorial part 4.
This code works as a GET request sent to my Strongloop API with a simple database model, however:
This works, but I don't know why it works, since it invokes no method that I can see to actually send the request.
I see no means to make it into a POST request.
My question is: How do I perform a POST request? Is it done in a completely different way?
Let me know if you need more information.
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func getFromDB() {
let url = urlWithSearchText("")
println("URL: '\(url)'")
if let jsonString = performGetRequestWithURL(url) {
println("Received JSON string '\(jsonString)'")
}
}
func urlWithSearchText(searchText: String) -> NSURL {
let escapedSearchText = searchText.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)!
let urlString = String(format: "http://localhost:3000/api/Tests", escapedSearchText)
let url = NSURL(string: urlString)
return url!
}
func performGetRequestWithURL(url: NSURL) -> String? {
var error: NSError?
if let resultString = String(contentsOfURL: url, encoding: NSUTF8StringEncoding, error: &error) {
return resultString
} else if let error = error {
println("Download Error: \(error)")
} else {
println("Unknown Download Error")
}
return nil
}
Here is a picture of this working:
https://dl.dropboxusercontent.com/u/14464971/Images/Messages%20Image%281477993527%29.png
Swift 3 & above
GET
func getRequest() {
// request url
let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1")! // change the url
// create URLSession with default configuration
let session = URLSession.shared
// create dataTask using the session object to send data to the server
let task = session.dataTask(with: url) { data, response, error in
if let error = error {
print("GET 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 {
// serialise the data object into Dictionary [String : Any]
if let jsonResponse = try JSONSerialization.jsonObject(with: responseData, options: .mutableContainers) as? [String: Any] {
print(jsonResponse)
} else {
print("data maybe corrupted or in wrong format")
throw URLError(.badServerResponse)
}
} catch let error {
print("JSON Parsing Error: \(error.localizedDescription)")
}
}
// resume the task
task.resume()
}
POST
func postRequest() {
// declare the parameter as a dictionary that contains string as key and value combination. considering inputs are valid
let parameters: [String: Any] = ["name": "abc", "password": "password#123"]
// create the url with URL
let url = URL(string: "http://myServerName.com/api")! //change the url
// create the session object
let session = URLSession.shared
// now create the URLRequest object using the url object
var request = URLRequest(url: url)
request.httpMethod = "POST" //set http method as POST
// add headers for the request
request.addValue("application/json", forHTTPHeaderField: "Content-Type") // change as per server requirements
request.addValue("application/json", forHTTPHeaderField: "Accept")
do {
// convert parameters to Data and assign dictionary to httpBody of request
request.httpBody = try JSONSerialization.data(withJSONObject: parameters, options: .prettyPrinted)
} catch let error {
print(error.localizedDescription)
return
}
// 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: Any] {
print(jsonResponse)
// handle json response
} else {
print("data maybe corrupted or in wrong format")
throw URLError(.badServerResponse)
}
} catch let error {
print(error.localizedDescription)
}
}
task.resume()
}
Below are two POST methods. Depending on if you want it synchronous (everything else waits until the post method is completed) or asynchronous (POST method runs in background, other methods run in parallel).
Methods
// POST data to url
func postDataAsynchronous(url: String, bodyData: String, completionHandler: (responseString: String!, error: NSError!) -> ()) {
var URL: NSURL = NSURL(string: url)!
var request:NSMutableURLRequest = NSMutableURLRequest(URL:URL)
request.HTTPMethod = "POST";
request.HTTPBody = bodyData.dataUsingEncoding(NSUTF8StringEncoding);
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()){
response, data, error in
var output: String!
if data != nil {
output = NSString(data: data, encoding: NSUTF8StringEncoding) as! String
}
completionHandler(responseString: output, error: error)
}
}
// Obtain the data
func postDataSynchronous(url: String, bodyData: String, completionHandler: (responseString: String!, error: NSError!) -> ())
{
let URL: NSURL = NSURL(string: url)!
var request:NSMutableURLRequest = NSMutableURLRequest(URL:URL)
request.HTTPMethod = "POST"
request.HTTPBody = bodyData.dataUsingEncoding(NSUTF8StringEncoding);
request.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
var response: NSURLResponse?
var error: NSError?
// Send data
let data = NSURLConnection.sendSynchronousRequest(request, returningResponse: &response, error: &error)
var output: String! // Default to nil
if data != nil{
output = NSString(data: data!, encoding: NSUTF8StringEncoding) as! String
}
completionHandler(responseString: output, error: error)
}
Using them
You can then call (use) them like so:
postDataSynchronous(url, bodyData: bodyData) {
responseString, error in
if error != nil {
println("Error during post: \(error)")
return
}
else{
//Success
println(responseString)
userType = responseString // Set usertype based on server response
}
}
SWIFT 2.0
func postData(url: String, params: Dictionary<String, String>, completionHandler: (data: NSData?, response: NSURLResponse?, error: NSError?) -> ()) {
// Indicate download
UIApplication.sharedApplication().networkActivityIndicatorVisible = true
let url = NSURL(string: url)!
// print("URL: \(url)")
let request = NSMutableURLRequest(URL: url)
let session = NSURLSession.sharedSession()
request.HTTPMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")
// Verify downloading data is allowed
do {
request.HTTPBody = try NSJSONSerialization.dataWithJSONObject(params, options: [])
} catch let error as NSError {
print("Error in request post: \(error)")
request.HTTPBody = nil
} catch {
print("Catch all error: \(error)")
}
// Post the data
let task = session.dataTaskWithRequest(request) { data, response, error in
completionHandler(data: data, response: response, error: error)
// Stop download indication
UIApplication.sharedApplication().networkActivityIndicatorVisible = false // Stop download indication
}
task.resume()
}
guard let url = URL(string: "https://jsonplaceholder.typicode.com/users") else { return }
let session = URLSession.shared
session.dataTask(with: url) { (data, response, error) in
if let response = response {
print(response)
}
if let data = data {
print(data)
do {
let json = try JSONSerialization.jsonObject(with: data, options: [])
print(json)
} catch {
print(error)
}
}
}.resume()
}
It's a get method.
This method invokes the http request.
String(contentsOfURL: url, encoding: NSUTF8StringEncoding, error: &error)
Because Swift String has no init signature like this.
This method would be written somewhere in the project, as extension of String
It would be something like this
extension String{
init(contentsOfURL: NSURL, encoding: NSUTF8StringEncoding, inout error: NSError){
// load data from url
self = //parse data to string
}
}
The String(contentsOfUrl:encoding:error) initializer makes a GET request under the hood and returns the content as a string with the specified encoding.
One way to make a request would be to create an NSURLConnection and use NSMutablrURLRequest set the HTTP method the post. With the NSMutableURLRequest, you can create a NSURLConnection and start it immediately with a delegate or you can call NSURLConnection.sendSynchronousRequest or NSURLConnection.sendAsynchronousRequest to send the request.
let parameters = ["username": "#Bipin_kumar", "tweet": "HelloWorld"]
guard let url = URL(string: "https://jsonplaceholder.typicode.com/posts") else { return }
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
guard let httpBody = try? JSONSerialization.data(withJSONObject: parameters, options: []) else { return }
request.httpBody = httpBody
let session = URLSession.shared
session.dataTask(with: request) { (data, response, error) in
if let response = response {
print(response)
}
if let data = data {
do {
let json = try JSONSerialization.jsonObject(with: data, options: [])
print(json)
} catch {
print(error)
}
}
}.resume()
It's a post method.
GET Request
func getRequest(with url: URL, callback: #escaping (Any?) -> Swift.Void) -> Void {
let defaultConfigObject = URLSessionConfiguration.default
defaultConfigObject.timeoutIntervalForRequest = 30.0
defaultConfigObject.timeoutIntervalForResource = 60.0
let session = URLSession.init(configuration: defaultConfigObject, delegate: nil, delegateQueue: nil)
var urlRequest = URLRequest(url: url as URL)
urlRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
urlRequest.httpMethod = "GET"
session.dataTask(with: urlRequest, completionHandler: { (data, response, error) in
guard let httpResponse: HTTPURLResponse = response as? HTTPURLResponse
else {
print("Error: did not receive data")
return
}
var response : (Any)? = nil
if httpResponse.statusCode == 200 {
print(httpResponse)
guard let responseData = data else {
print("Error: did not receive data")
return
}
do {
let responseData = try JSONSerialization.jsonObject(with: responseData, options: [JSONSerialization.ReadingOptions.allowFragments])
response = responseData
callback(response)
}
catch _ as NSError {
let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
callback(responseString)
return
}
}
else {
print(httpResponse)
guard error == nil else {
print("error calling GET on /todos/1")
print(error ?? "error")
callback(response!)
return
}
}
}).resume()
}
POST REQUEST
//MARK: post request
func postRequest(with url:URL, postBody:String, callback: #escaping (Any?) -> Void) -> Void {
let defaultConfigObject = URLSessionConfiguration.default
defaultConfigObject.timeoutIntervalForRequest = 30.0
defaultConfigObject.timeoutIntervalForResource = 60.0
let session = URLSession.init(configuration: defaultConfigObject, delegate: nil, delegateQueue: nil)
let params: String! = postBody
var urlRequest = URLRequest(url: url as URL)
urlRequest.httpMethod = "POST"
let data = params.data(using: String.Encoding(rawValue: String.Encoding.utf8.rawValue))
urlRequest.httpBody = data
session.dataTask(with: urlRequest, completionHandler: { (data, urlResponse, error) in
guard let httpResponse:HTTPURLResponse = urlResponse as? HTTPURLResponse
else{
print("did not get any data")
return
}
var response : (Any)? = nil
if httpResponse.statusCode == 200 {
guard let responseData = data else {
print("Error: did not receive data")
return
}
do {
guard let responseData = try JSONSerialization.jsonObject(with: responseData, options: []) as? [String: AnyObject] else {
print("error trying to convert data to JSON")
return
}
response = responseData
callback(response)
} catch _ as NSError {
let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
callback(responseString)
return
}
}
else {
guard error == nil else {
print("error calling GET on /todos/1")
print(error ?? "error")
callback(nil)
return
}
}
}).resume()
}
Always try to check the HTTPURLResponse code