tabBarController 點擊某個按鈕不生效

//tabBarController 點擊某個按鈕不生效
#pragma mark UITabBarControllerDelegate
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController
{
    if ([viewController isEqual:middleBtn]) {
        return NO;
    }
    return YES;
}