DYLD: Symbole non trouvé: Erreur Comment résoudre ce problème

J'ai le code suivant (donné ci-dessous) où j'utilise nsurlconnection code> pour connecter et analyser la chaîne de réponse. Mais je reçois l'erreur suivante:

@implementation Websample1ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
    dataWebService = [[NSMutableData data] retain];
    NSMutableURLRequest *request = [[NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"https://www.googleapis.com/customsearch/v1?key=AIzaSyDzl0Ozijg2C47iYfKgBWWkAbZE_wCJ-2U&cx=017576662512468239146:omuauf_lfve&q=lectures&callback=handleResponse"]]retain];    

    NSURLConnection *myConnection = [NSURLConnection connectionWithRequest:request delegate:self];
    [myConnection start];
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
{
    [dataWebService setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [dataWebService appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection 
{
    NSString *responseString = [[NSString alloc] initWithData:dataWebService encoding:NSUTF8StringEncoding];
    NSLog(@"Response: %@",responseString);
    [responseString release];
    [dataWebService release];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"Error during connection: %@", [error description]);
}

//class 2
@implementation WebJson
//parse JSON
- (void)requestCompleted:(ASIHTTPRequest *)request
{
    NSString *responseString = [request responseString];   
    NSDictionary *dictionary = [responseString JSONValue];
    NSDictionary *dictionaryReturn = (NSDictionary*) [dictionary objectForKey:@"request"];    
    NSString *total = (NSString*) [dictionaryReturn objectForKey:@"totalResults"];
    NSLog(@"totalResults: %@", total); 

    NSString *search = (NSString*) [dictionaryReturn objectForKey:@"searchTerms"];
    NSLog(@"searchTerms: %@", search);       

    int count = [[dictionaryReturn objectForKey:@"count"] intValue];
    NSLog(@"count: %d", count);
}