IOS获取当前所在的ViewController

这个主要用于给别人提供的API中，有关跳转的地方。在IOS中，跳转必须提供目前所在的ViewController。代码如下：

// 获取当前显示的 UIViewController
+ (UIViewController *)dc_findCurrentShowingViewController {
    //获得当前活动窗口的根视图
    UIViewController *vc = [UIApplication sharedApplication].keyWindow.rootViewController;
    UIViewController *currentShowingVC = [self findCurrentShowingViewControllerFrom:vc];
    return currentShowingVC;
}
+ (UIViewController *)findCurrentShowingViewControllerFrom:(UIViewController *)vc
{
    // 递归方法 Recursive method
    UIViewController *currentShowingVC;
    if ([vc presentedViewController]) {
        // 当前视图是被presented出来的
        UIViewController *nextRootVC = [vc presentedViewController];
        currentShowingVC = [self findCurrentShowingViewControllerFrom:nextRootVC];

    } else if ([vc isKindOfClass:[UITabBarController class]]) {
        // 根视图为UITabBarController
        UIViewController *nextRootVC = [(UITabBarController *)vc selectedViewController];
        currentShowingVC = [self findCurrentShowingViewControllerFrom:nextRootVC];

    } else if ([vc isKindOfClass:[UINavigationController class]]){
        // 根视图为UINavigationController
        UIViewController *nextRootVC = [(UINavigationController *)vc visibleViewController];
        currentShowingVC = [self findCurrentShowingViewControllerFrom:nextRootVC];

    } else {
        // 根视图为非导航类
        currentShowingVC = vc;
    }

    return currentShowingVC;
}