Starting February 1, 2015, new iOS apps uploaded to the App Store must include 64-bit support and be built with the iOS 8 SDK, included in Xcode 6 or later. To enable 64-bit in your project, we recommend using the default Xcode build setting of “Standard architectures” to build a single binary with both 32-bit and 64-bit code.
从2015年2月1日起，新的iOS的App上传到App Store 必须支持64-bit 和iOS8,包括Xcode6及后续版本，确保64 bit在你的项目是可用的，我们建议使用Standard architectures设置来构建包含32、64 bit 编码方式。
原文：http://blog.csdn.net/xietao3/article/details/40424499