ios Undefined symbols for architecture arm64:错误解决

使用cocoapod加入第三方库，打开项目有时会出现编译错误，错误如下 
Undefined symbols for architecture x86_64:  "_OBJC_CLASS_$_AFHTTPRequestOperationManager", referenced from:      objc-class-ref in AFNetworkingUtil.old: symbol(s) not found for architecture x86_64clang: error: linker command failed with exit code 1 (use -v to see invocation)



1、AFNetworkingUtil 是自己写的一个类，类中用到了 pod中AFNetworking框架的头文件
2、出现编译错误在stackoverflow找到这个问答 http://stackoverflow.com/questions/19213782/undefined-symbols-for-architecture-arm64?rq=1

3、解决步骤 
  a、Build Setting -> Architectures & Valid Architectures 检查配置是否正确



  b、确认如图无误，再 在 Build Setting -> linking 加入以下配置