Can I somehow do a synchronous HTTP request via NSURLSession in Swift

Question

Can I somehow do a synchronous HTTP request via NSURLSession in Swift?

I can do an asynchronous request via the following code:

if let url = NSURL(string: "https://2ch.hk/b/threads.json") {             let task = NSURLSession.sharedSession().dataTaskWithURL(url) {                 (data, response, error) in                  var jsonError: NSError?                 let jsonDict = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonError) as [String: AnyObject]                 if jsonError != nil {                     return                 }                  // ...             }             task.resume()         } 

But what about synchronous request?

Answer 1

You can use this NSURLSession extension to add a synchronous method:

extension NSURLSession {     func synchronousDataTaskWithURL(url: NSURL) -> (NSData?, NSURLResponse?, NSError?) {         var data: NSData?, response: NSURLResponse?, error: NSError?          let semaphore = dispatch_semaphore_create(0)          dataTaskWithURL(url) {             data = $0; response = $1; error = $2             dispatch_semaphore_signal(semaphore)         }.resume()          dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)          return (data, response, error)     } } 

Update for Swift 3:

extension URLSession {     func synchronousDataTask(with url: URL) -> (Data?, URLResponse?, Error?) {         var data: Data?         var response: URLResponse?         var error: Error?          let semaphore = DispatchSemaphore(value: 0)          let dataTask = self.dataTask(with: url) {             data = $0             response = $1             error = $2              semaphore.signal()         }         dataTask.resume()          _ = semaphore.wait(timeout: .distantFuture)          return (data, response, error)     } } 

Answer 2

Apple thread discussing the same issue.

+ (NSData *)sendSynchronousRequest:(NSURLRequest *)request       returningResponse:(__autoreleasing NSURLResponse **)responsePtr       error:(__autoreleasing NSError **)errorPtr {       dispatch_semaphore_t    sem;       __block NSData *        result;        result = nil;        sem = dispatch_semaphore_create(0);        [[[NSURLSession sharedSession] dataTaskWithRequest:request           completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {           if (errorPtr != NULL) {               *errorPtr = error;           }           if (responsePtr != NULL) {               *responsePtr = response;           }           if (error == nil) {               result = data;           }           dispatch_semaphore_signal(sem);       }] resume];        dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);       return result;   }   

Answer by Quinn "The Eskimo!" Apple Developer Relations, Developer Technical Support, Core OS/Hardware