Swift pod报错

问题 Undefined symbols for architecture x86_64:

"_swift_getFieldAt", referenced from:
HandyJSON.Metadata.Class._propertyDescriptionsAndStartPoint() -> ([HandyJSON.Property.Description], Swift.Int32?)? in Metadata.o
HandyJSON.Metadata.Struct.propertyDescriptions() -> [HandyJSON.Property.Description]? in Metadata.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

解决办法
1.删除pod文件内容 pod install
2.重新加入库 pod install  
3.如果失败的话，那么删除pod文件内容 pod install
4.更新 pod repo update
5.重新导入库