编辑为包含您需要采取的两个可能的步骤:

Edited to include two possible steps you need to take:

1. 确保您的项目具有 Foundation 框架.(消除并再次添加以确保).
2. 确保基础框架包含在CFNetwork之前.

1. Make sure you have Foundation framework to your project. (Remove and add it again to be sure).
2. Make sure the Foundation framework include is before CFNetwork.

iOS8.0 中的标头包含的内容似乎发生了变化(例如，glextensions 文件不再位于顶部标头中).如果您显式地将 Foundation 框架添加到您的项目中，它将很好地构建.当然，将 CFNetwork 设为可选会导致失败，并且只是构建错误的解决方案，而不是整体解决方案.

There seems to be a change in which headers include what in iOS8.0 (the glextensions file, for example, is no longer in the top header). If you explicitly add Foundation framework to your project, it will build fine. Making CFNetwork optional will, of course, lead to failures and is only a solution for the build error and not a solution overall.