UISearchBar取消按钮不可用的解决方法

UISearchBar失去焦点时取消按钮会不可用，我们可以在UISearchBar失去焦点时(例如点击搜索，拖动滚动条等)，将取消按钮isEnabled设置为true，使用KVC不会导致App Store审核被拒。

extension UISearchBar{
    func setCancelButtonEnable(){
        if let cancelButton = value(forKey: "cancelButton") as? UIButton{
            cancelButton.isEnabled = true
        }
    }
}

    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
        searchBar.resignFirstResponder()
        searchBar.setCancelButtonEnable()
    }
    
    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        searchBar.resignFirstResponder()
        searchBar.setCancelButtonEnable()
    }