如何使 initWithNibName 表现得像 instantiateViewControllerWithIdentifier

Question

我正在尝试将视图控制器容器 library 添加到 remail 电子邮件客户端。这个想法是视图控制器容器presents its child view controllers in two layers. It provides functionality for sliding the top view to reveal the views underneath it.

在库描述中，这是将子 controllerView 附加到其父级的建议方法：

if (![self.slidingViewController.underLeftViewController 
        isKindOfClass:[MenuViewController class]]) {
    self.slidingViewController.underLeftViewController  = 
        [self.storyboard instantiateViewControllerWithIdentifier:@"Menu"];
  }

其中 slidingViewController 是 the top-level instance of the view controller container. With this instance, you can set the view controllers underneath the top view and add panning.

我使用的是 xib 文件，而不是楼层板。所以我的代码看起来像这样：

if (![self.slidingViewController.underLeftViewController 
        isKindOfClass:[MenuViewController class]]) {
    self.slidingViewController.underLeftViewController  =
         [[MenuViewController alloc] initWithNibName:@"Menu" bundle:nil];
}

但使用该代码.. 我收到此错误：
-[__NSArrayM insertObject:atIndex:]: object cannot be nil

可以追踪到slidingViewController 执行以下操作：
[self.view insertSubview:_underTopViewController.view atIndex:0];

查看文档。我发现instantiateViewControllerWithIdentifier 和initWithNibName 之间存在差异：前者始终返回一个对象。而后者仅加载the first time the view controller’s view is accessed。

问题：如何让 initWithNibName 返回一个加载的 viewcontroller 对象，无论该视图是否已被访问......类似于 instantiateViewControllerWithIdentifier？

Answer 1

您应该可以通过just accessing the view property 来触发它，例如；

if (![self.slidingViewController.underLeftViewController 
              isKindOfClass:[MenuViewController class]]) 
{
    MenuViewController *vc = 
      [[MenuViewController alloc] initWithNibName:@"Menu" bundle:nil];
    [vc view];  // <-- access the view and trigger loading
    self.slidingViewController.underLeftViewController  = vc;
}