跳转模态视图兼容ios4.3（NSClassFromString）

跳转模态视图兼容ios5，ios4.3

- (void)setWirless
{
    ConfigureWirelessViewController *vcConfigureWireless = [[ConfigureWirelessViewController alloc] init];
    vcConfigureWireless.m_delegateConfigureWireless = self;
    
    //创建Nav
    UINavigationController *navSetWireless = [[UINavigationController alloc] initWithRootViewController:vcConfigureWireless];
    
    navSetWireless.modalPresentationStyle = UIModalPresentationPageSheet;
    self.m_navSetWireless = navSetWireless;
    [navSetWireless release];
    
    //设置导航栏底图
    [ABUtil setNavigationCtrollerBackImg:m_navSetWireless];
    
    if ([NSClassFromString(@"UIViewController") instancesRespondToSelector:@selector(presentViewController:animated:completion:)])
    {
        [self presentViewController:m_navSetWireless animated:YES completion:nil];
    }
    else
    {
        [self presentModalViewController:m_navSetWireless animated:YES];
    }
    
    [vcConfigureWireless release];
}