让 UISearchBar 支持空搜索，当没有输入的时候，search 按钮一样可以点击

//让 UISearchBar 支持空搜索，当没有输入的时候，search 按钮一样可以点击

- (void)searchBarTextDidBeginEditing:(UISearchBar *) searchBar

{

    UITextField *searchBarTextField = nil;

    NSArray *views = ([[[UIDevice currentDevice] systemVersion] floatValue] < 7.0) ? searchBar.subviews : [[searchBar.subviews objectAtIndex:0] subviews];

    for (UIView *subview in views)

    {

        if ([subview isKindOfClass:[UITextField class]])

        {

            searchBarTextField = (UITextField *)subview;

            break;

        }

    }

    searchBarTextField.enablesReturnKeyAutomatically = NO;

}