CODEWITHSUNDEEP
iosobjective-cnsurlsession
Changerrs
Changerrs

Reputation: 273

NSURLSessionDataTask delegate methods are not called

I am trying to download some JSON from an API. Right now nothing gets printed.

I know for sure that the path and the API Key/Value works, because I did it with the NSURLSessionDataTask with the completion handler, but I wanted to learn about how to do the same with delegate methods.

But I cant seem to figure out why my delegate methods are not called.

@interface MetaData () <NSURLSessionDelegate, NSURLSessionDataDelegate>

@end

@implementation MetaData
-(void)downloadData
{
    NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];

    [sessionConfig setHTTPAdditionalHeaders:@{ header : key}];
    NSURLSession *defaultSesh = [NSURLSession sessionWithConfiguration:sessionConfig];
    NSURLSessionDataTask *dataTask = [defaultSesh dataTaskWithURL:[NSURL URLWithString:path]];
    defaultSesh = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];
    [dataTask resume];


}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
{
    NSLog(@"here 2");
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{
    NSLog(@"here");
    _weaponDictionary = [NSJSONSerialization JSONObjectWithData:data
                                                        options:kNilOptions
                                                          error:nil];
    NSLog(@"dictionary: %@", _weaponDictionary);
}

Thanks for the help.

EDIT

defaultSesh = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];

by adding that line, i set the delegate to self. So now I print "here 2" but still dont print the dictionary...

Upvotes: 0

Views: 6038

Answers (3)

Shruti
Shruti

Reputation: 131

Faced a similar issue and was stuck for a really long time when I finally got the answer. Hope it helps for those who search for a similar issue

Swift

// create a URLSessionConfiguration object

`let config = URLSessionConfiguration.default
 config.requestCachePolicy = .reloadIgnoringLocalCacheData
 mySession = URLSession(configuration: config, delegate: self, delegateQueue: OperationQueue.main)`

// make a request 

`let myTask = mySession.dataTask(with: request as URLRequest , completionHandler: { (data: Data?, response: URLResponse?, error:Error?) in
        if let error = error {
            print(error.localizedDescription)
        }
        else{
            print(response)
        }
    })
    myTask.resume()`

// if there is a redirect required implement the delegate method

`func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest, completionHandler: @escaping (URLRequest?) -> Void) {

var newRequest = URLRequest(url:(request.url?.absoluteURL)!)`

// take the URL request from the delegate method and make a new task to begin

 `let newDataTask = nestSession.dataTask(with: newRequest)
  newDataTask.resume()

}`

// implement the delegate methods to capture the data

`func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
    NSLog("task data: %@", data as NSData)
}`

Upvotes: 0

Roshan Sah
Roshan Sah

Reputation: 137

You have to set delegate first in viewDidload

id <NSURLSessionDelegate> delegate = [[Your_ViewController alloc]init];

Upvotes: -1

vadian
vadian

Reputation: 285079

Use the method

+ (NSURLSession *)sessionWithConfiguration:(NSURLSessionConfiguration *)configuration
                                  delegate:(id<NSURLSessionDelegate>)delegate
                             delegateQueue:(NSOperationQueue *)queue

to set the delegate properly.

Update:

And you have to call the completion handler of didReceiveResponse

completionHandler

A completion handler that your code calls to continue the transfer, passing a constant to indicate whether the transfer should continue as a data task or should become a download task.
• If you pass NSURLSessionResponseAllow, the task continues normally.
• If you pass NSURLSessionResponseCancel, the task is canceled.
• If you pass NSURLSessionResponseBecomeDownload as the disposition, your delegate’s URLSession:dataTask:didBecomeDownloadTask: method is called to provide you with the new download task that supersedes the current task.

For example

- (void) URLSession:(NSURLSession *)session 
           dataTask:(NSURLSessionDataTask *)dataTask 
 didReceiveResponse:(NSURLResponse *)response 
  completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
    completionHandler(NSURLSessionResponseAllow);
}

Upvotes: 5

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