iOS_修改UISearchBar背景为透明色

for (UIView *subview in searchBar.subviews) {
        for(UIView* grandSonView in subview.subviews){
            if ([grandSonView isKindOfClass:NSClassFromString(@"UISearchBarBackground")]) {
                grandSonView.alpha = 0.0f;
            }else if([grandSonView isKindOfClass:NSClassFromString(@"UISearchBarTextField")] ){
                NSLog(@"Keep textfiedld bkg color");
            }else{
                grandSonView.alpha = 0.0f;
            }
        }
    }