[摘要]本文是對AFNetworking報錯"_UTTypeCopyPreferredTagWithClass", referenced from: _AFContentTypeForPathExtens的講解，對學習IOS蘋果軟件開發有所幫助,與大家分享。

問題： 在和Unity交互的過程中，從Unity開發工具打包出來的項目文件，在添加AFNetworking庫，運行時報出以下錯誤：

Undefined symbols for architecture armv7:

"_kUTTagClassMIMEType", referenced from:

-[AFStreamingMultipartFormData appendPartWithFileURL:name:error:] in AFURLRequestSerialization.o

"_kUTTagClassFilenameExtension", referenced from:

-[AFStreamingMultipartFormData appendPartWithFileURL:name:error:] in AFURLRequestSerialization.o

"_UTTypeCreatePreferredIdentifierForTag", referenced from:

-[AFStreamingMultipartFormData appendPartWithFileURL:name:error:] in AFURLRequestSerialization.o

"_UTTypeCopyPreferredTagWithClass", referenced from:

-[AFStreamingMultipartFormData appendPartWithFileURL:name:error:] in AFURLRequestSerialization.o

ld: symbol(s) not found for architecture armv7

clang: error: linker command failed with exit code 1 (use -v to see invocation)

原因是未添加 MobileCoreServices.framework（此框架定義統一類型標識符 (UTIs)使用的底層類型）

解決：Build Phase ->Link Binary With Libraries()下添加MobileCoreServices.framework。添加成功後運行程序成功。