I am not sure try this,
change the url format to this in your code and check
[NSURL URLWithString:[NSString stringWithFormat:@"http://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=%@&text=%@&per_page=20&format=json&nojsoncallback=1",kFlickrAPIKey,searchTerm]];
where,searchTerm string what u are searching