Swift: error: linker command failed with exit code 1

There are similar questions, but none that answer my question. I am using Swift 2.0 I am working on a project that shows longitude and latitude using CoreLocation. I also am using the Social framework to post to twitter and facebook. I am getting an error that says "error: linker command failed with exit code 1 " and then it tells me "(use -v to see invocation)" but I do not understand that. I am going off an answer here on SO to write the location services portion. here is the link http://stackoverflow.com/a/24696878/6140339 here is my code: import UIKit import Social import CoreLocation @UIApplicationMain class FirstViewController: UIViewController, CLLocationManagerDelegate, UIApplicationDelegate { var window: UIWindow? var locationManager: CLLocationManager! var seenError : Bool = false var locationFixAchieved: Bool = false var locationStatus : NSString = "Not Started" func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject : AnyObject]?) -> Bool { initLocationManager(); return true } func initLocationManager() { seenError = false locationFixAchieved = false locationManager = CLLocationManager() locationManager.delegate = self CLLocationManager.locationServicesEnabled() locationManager.desiredAccuracy = kCLLocationAccuracyBest locationManager.requestAlwaysAuthorization() } func locationManager(manager: CLLocationManager, didFailWithError error: NSError) { locationManager.stopUpdatingLocation() if (error == true) { if (seenError == false) { seenError = true print(error) } } } func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) { if (locationFixAchieved == false) { locationFixAchieved = true let locationArray = locations as NSArray let locationObj = locationArray.lastObject as! CLLocation let coord = locationObj.coordinate print(coord.latitude) print(coord.longitude) } } func locationManager(manager: CLLocationManager, didChangeAuthorizationStatus status: CLAuthorizationStatus) { var shouldIAllow = false switch status { case CLAuthorizationStatus.Restricted: locationStatus = "Restricted Access to location" case CLAuthorizationStatus.Denied: locationStatus = "User denied access to location" case CLAuthorizationStatus.NotDetermined: locationStatus = "Status not determined" default: locationStatus = "Allowed to location Access" shouldIAllow = true } NSNotificationCenter.defaultCenter().postNotificationName("LabelHasBeenUpdated", object: nil) if (shouldIAllow == true) { NSLog("Location to Allowed") //Start location services locationManager.startUpdatingLocation() } else { NSLog("Denied access: (locationStatus)") } } @IBAction func postToFacebookButton(sender: UIButton) { if(SLComposeViewController.isAvailableForServiceType(SLServiceTypeFacebook)){ let socialController = SLComposeViewController(forServiceType: SLServiceTypeFacebook) //creates post with pre-desired text socialController.setInitialText("") self.presentViewController(socialController, animated: true, completion: nil) } } @IBAction func postTweetButton(sender: UIButton) { if(SLComposeViewController.isAvailableForServiceType(SLServiceTypeTwitter)){ let socialController = SLComposeViewController(forServiceType: SLServiceTypeTwitter) //creates post with pre-desired text socialController.setInitialText("") self.presentViewController(socialController, animated: true, completion: nil) } } override func preferredStatusBarStyle() -> UIStatusBarStyle { return .LightContent } override func viewDidLoad() { super.viewDidLoad() } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } //layer.cornerRadius layer.cornerRadius } Entire error message: duplicate symbol _main in: /Users/user/Library/Developer/Xcode/DerivedData/FarOut-ekrxzlgzfahpruavmlhyhiwiynum/Build/Intermediates/FarOut.build/Debug-iphonesimulator/FarOut.build/Objects-normal/x86_64/AppDelegate.o /Users/user/Library/Developer/Xcode/DerivedData/FarOut-ekrxzlgzfahpruavmlhyhiwiynum/Build/Intermediates/FarOut.build/Debug-iphonesimulator/FarOut.build/Objects-normal/x86_64/FirstViewController.o ld: 1 duplicate symbol for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)