iOS _OBJC_CLASS_$_ASIdentifierManage referenced from: objc-class-ref in ViewController.o

I am trying to launch a WebView in iOS and transmit the IDFA as part of a GET request but when I try to build it fails and I get the following error: ``` Undefined symbols for architecture i386: "_OBJC_CLASS_$_ASIdentifierManager", referenced from: objc-class-ref in ViewController.o ld: symbol(s) not found for architecture i386 clang: error: linker command failed with exit code 1 (use -v to see invocation) ``` Here is the code I have. Any idea what I'm doing wrong here, I am a bit stuck ``` #import "ViewController.h" #import "AdSupport/ASIdentifierManager.h" @interface ViewController () @end @implementation ViewController @synthesize webView; - (void)viewDidLoad { NSString *idfaString = [[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString]; webView.backgroundColor = [UIColor blueColor]; NSURL *url = [NSURL URLWithString:@"http://example.com/"]; NSString *param = [url.path stringByAppendingString: idfaString]; NSURL *send = [[NSURL alloc] initWithString:param]; NSURLRequest *req = [NSURLRequest requestWithURL:send]; [webView loadRequest:req]; [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } @end ```