ios – 如何使用NSCache

概述有人可以举例说明如何使用NSCache缓存字符串？ 或任何人有一个链接到良好的解释？我似乎找不到任何.. 你使用它与使用NSMutableDictionary的方式相同。不同的是，当NSCache检测到过大的内存压力(即它缓存太多的值)，它将释放一些值，以腾出空间。 如果你可以在运行时重新创建这些值(通过从互联网下载，通过计算，任何)，那么NSCache可能适合你的需要。如果数据不能被重新创建(例 有人可以举例说明如何使用NSCache缓存字符串？
或任何人有一个链接到良好的解释？我似乎找不到任何..解决方法 你使用它与使用NSMutableDictionary的方式相同。不同的是，当NSCache检测到过大的内存压力(即它缓存太多的值)，它将释放一些值，以腾出空间。

如果你可以在运行时重新创建这些值(通过从互联网下载，通过计算，任何)，那么NSCache可能适合你的需要。如果数据不能被重新创建(例如它的用户输入，它是时间敏感的等)，那么你不应该将它存储在NSCache中，因为它将被销毁。

例如，不考虑线程安全：

// Your cache should have a lifetime beyond the method or handful of methods// that use it. For example,you Could make it a fIEld of your application// delegate,or of your vIEw controller,or something like that. Up to you.NSCache *myCache = ...;NSAssert(myCache != nil,@"cache object is missing");// Try to get the existing object out of the cache,if it's there.Widget *myWidget = [myCache objectForKey: @"important Widget"];if (!myWidget) {    // It's not in the cache yet,or has been removed. We have to    // create it. Presumably,creation is an expensive operation,// which is why we cache the results. If creation is cheap,we    // probably don't need to bother caching it. That's a design    // decision you'll have to make yourself.    myWidget = [[[Widget alloc] initExpensively] autorelease];    // Put it in the cache. It will stay there as long as the OS    // has room for it. It may be removed at any time,however,// at which point we'll have to create it again on next use.    [myCache setobject: myWidget forKey: @"important Widget"];}// myWidget should exist Now either way. Use it here.if (myWidget) {    [myWidget runorWhatever];}

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