NSURLSession+Synchronous.swift

extension NSURLSession {
    
    class func sendSynchronousRequest(request: NSURLRequest, inout returningResponse: NSHTTPURLResponse?, inout error: NSError?) -> NSData? {
        
        var data: NSData?
        var sem: dispatch_semaphore_t
        
        sem = dispatch_semaphore_create(0)
        
        NSURLSession.sharedSession().dataTaskWithRequest(request) { (requestData, requestResponse, requestError) in
            if let _requestError = requestError {
                error = _requestError
            }
            
            if let _requestResponse = requestResponse {
                returningResponse = _requestResponse as? NSHTTPURLResponse
            }
            
            if error == nil {
                data = requestData
            }
            
            dispatch_semaphore_signal(sem)
        }.resume()
        
        dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER)
        
        return data
    }
    
}