关于Storyboard拖拽的ViewController返回上一层时有对象被释放

   最近有个需求，设置播放器播放音频时，要求离开当前播放页面也是可以播放的，然后整个项目都是采用storyboard拖拽，播放器设置是采用KVO通知的，当我点击返回时，发现播放器控制对象被释放了，然后导致程序崩溃。于是发现了在storyboard中拖拽的ViewController采用push或者modal弹出时，当点击返回离开当前页面时，strong类型修饰的变量被释放，于是采用代码形式初始化播放页面的ViewController.详见如下代码：

@property (nonatomic,strong)CoursePlayViewController *courseVC;

- (void)enterPlayViewController

{
    if (!self.courseVC) {
        self.courseVC = [[CoursePlayViewController alloc] init];
    }
    [[self getCurrentVC] presentViewController:self.courseVC animated:YES completion:nil];

}

- (UIViewController *)getCurrentVC
{
    UIViewController *result = nil;
    
    UIWindow * window = [[UIApplication sharedApplication] keyWindow];
    if (window.windowLevel != UIWindowLevelNormal)
    {
        NSArray *windows = [[UIApplication sharedApplication] windows];
        for(UIWindow * tmpWin in windows)
        {
            if (tmpWin.windowLevel == UIWindowLevelNormal)
            {
                window = tmpWin;
                break;
            }
        }
    }
    
    UIView *frontView = [[window subviews] objectAtIndex:0];
    id nextResponder = [frontView nextResponder];
    if ([nextResponder isKindOfClass:[UIViewController class]])
        result = nextResponder;
    else
        result = window.rootViewController;
    return result;
}

[self getCurrentVC] 是获取当前页面的视图控制器的方法。