NSCache - 标记对象不可移除 [英] NSCache - marking object not-removable

问题描述

当用户通过菜单在视图控制器之间切换时，如果他有足够的内存，我想缓存它们。为了这样做，我想使用 NSCache 来存储许多 UIViewControllers 。

When user switches between view controllers via menu, I want to cache them if he has enough memory. In order to do so, I want to use NSCache to store many UIViewControllers.

然而，我不知道如何告诉 NSCache 当前对象当前正在使用，不应该删除。
例如，当我运行app，加载少数视图控制器并退出应用程序时， NSCache 自动删除所有 viewControllers （这是有道理的 - 应用程序将能够在前台保持更长时间）。

However, I'm not sure how I can tell NSCache that current object is currently used and should not be removed. E.g, when I run app, load few view controllers and quit the app, NSCache automatically delete all viewControllers (which makes sense - app will be able to stay longer in the foreground). However, it also removes currently displayed view controller which is not what I wanted.

如何将特定对象标记为不可移除？

How can I mark particular object as not-removable?

推荐答案

您可以这样做：

当应用程序转到背景时，缓存将被删除。
所以当应用程序进行后台存储数据从缓存到{NSUserDefaults}和应用程序didBecomeActive重新分配值到缓存。

The cache will be removed when the application goes to background. So when the application goes background store the data from cache to {NSUserDefaults} and when application didBecomeActive reassign the value to cache.

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