获取当前的控制器

做项目时经常要获取到当前控制器来进行一些操作，故用下边的方法可以获取到

+ (UIViewController *)getCurrentVC {

    UIWindow *window = [[UIApplication sharedApplication].windows firstObject];
    if (!window) {
        return nil;
    }
    UIView *tempView;
    for (UIView *subview in window.subviews) {
        if ([[subview.classForCoder description] isEqualToString:@"UILayoutContainerView"]) {
            tempView = subview;
            break;
        }
    }
    if (!tempView) {
        tempView = [window.subviews lastObject];
    }

    id nextResponder = [tempView nextResponder];
    while (![nextResponder isKindOfClass:[UIViewController class]] || [nextResponder isKindOfClass:[UINavigationController class]] || [nextResponder isKindOfClass:[UITabBarController class]]) {
        tempView =  [tempView.subviews firstObject];

        if (!tempView) {
            return nil;
        }
        nextResponder = [tempView nextResponder];
    }
    return  (UIViewController *)nextResponder;
}