func collectionView(_ collectionView:UICollectionView,didSelectItemAt indexPath:IndexPath){
performSegue(withIdentifier: "detailVC", sender: self)
index = indexPath.row
passingObject = BookData.bookModels[index!]
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "detailVC" {
guard let destVC = segue.destination as? DetailVC else {return}
destVC.reciveData = passingObject
}
}