我今天在Xcode 4下将我的aaLuminate应用程序转换为Universal时出现了这个错误。 这个应用程序基于实用工具模板，最初是在Xcode 3下构建的。

为了节省时间，我将iPhone主视图和Flipside视图复制到Universal应用程序上的适当名称。我遇到了“Interface Builder file中未知类x”错误。在我的案例中，XIB文件或目标中没有任何内容。

我还复制了aaLuminate-Info。plist文件跨越其他原因-这有一个旧的关键“主nib文件基名”设置为MainWindow。

只要我删除这个关键它修复了问题!

在我的例子中，我有XCode6，指定的类.m文件最终在构建阶段的错误位置-它应该在编译源下，但最终在

这是一个Xcode4缓存问题，删除所有文件夹 /Users/your_user/Library/Application Support/iPhone Simulator/4.3/Applications/

此外，如果你在iPhone上测试时遇到同样的问题，在运行之前删除旧应用程序……

祝你好运。帕斯卡

In my case I got this error because I'd tried to save some work by creating a new project and then deleting several of the source files and copying over the source files of the same name from the working project. I also copied my MainStoryBoard file which was looking for my RootViewController. However, when I had deleted the original RootViewController and then added in the RootViewController from the previous product, evidently the Add Files operation failed to "check" the target box as suggested above. By merely visting all of the newley imported ".m" files and making sure that the target membership box was checked, all was well. I think what was happening was that the storyboard file was looking for a class that had been "excluded" from the link because the target membership was unchecked. Making sure the required files for the target are so designated in the target membership in the file inspector did the trick. Thanks Pat! (see above)

我在目标中添加了Build Phase文件，问题得到了解决。关于添加文件的步骤，请参阅我的回答:

Apple Mach-O连接器错误(APActivityIcon)

每个苹果文档

对于64位和iPhone操作系统应用程序，有一个链接器错误 阻止-ObjC从静态库中加载对象文件 只包含类别，不包含类。解决方法是使用 -all_load或-force_load标志。

简而言之，在你的“构建设置”中添加-all_load到“其他链接器”标志，你应该没问题。

http://developer.apple.com/library/mac/qa/qa1490/_index.html