iOS Undefined symbols for architecture arm64

Undefined symbols for architecture arm64:
  "_OBJC_CLASS_$_YYCache", referenced from:
      objc-class-ref in LFNetworking.o
  "_OBJC_CLASS_$_AFHTTPRequestSerializer", referenced from:
      objc-class-ref in LFNetworking.o
  "_OBJC_CLASS_$_AFJSONResponseSerializer", referenced from:
      objc-class-ref in LFNetworking.o
  "_OBJC_CLASS_$_AFHTTPSessionManager", referenced from:
      objc-class-ref in LFNetworking.o
ld: symbol(s) not found for architecture arm64

如果用CocoaPods导入的库，Build Setting->Linking->Other Linker Flags，添加$(inherited)