查看spark DataSet上的select()函数，有各种生成的函数签名：
(c1: TypedColumn[MyClass, U1],c2: TypedColumn[MyClass, U2] ....)
这似乎暗示我应该能够直接引用MyClass的成员并且类型安全，但我不确定如何......
ds.select("member")当然有效..似乎ds.select(_.member)也可能以某种方式起作用？
答案 0 :(得分：14)
在iOS/Pods/TwilioCommon/TwilioCommon.framework/TwilioCommon, file was built for unsupported file format ( 0x76 0x65 0x72 0x73 0x69 0x6F 0x6E 0x20 0x68 0x74 0x74 0x70 0x73 0x3A 0x2F 0x2F ) which is not the architecture being linked (x86_64): /Users/somendra/Documents/iOS/Pods/TwilioCommon/TwilioCommon.framework/TwilioCommon
iOS/Pods/TwilioConversationsClient/TwilioConversationsClient.framework/TwilioConversationsClient, file was built for unsupported file format ( 0x76 0x65 0x72 0x73 0x69 0x6F 0x6E 0x20 0x68 0x74 0x74 0x70 0x73 0x3A 0x2F 0x2F ) which is not the architecture being linked (x86_64): /Users/somendra/Documents/iOS/Pods/TwilioConversationsClient/TwilioConversationsClient.framework/TwilioConversationsClient
Undefined symbols for architecture x86_64:
"_OBJC_CLASS_$_TWCCameraCapturer", referenced from:
type metadata accessor for __ObjC.TWCCameraCapturer in TwilioManager.o
"_OBJC_CLASS_$_TWCConversation", referenced from:
type metadata accessor for __ObjC.TWCConversation in TwilioManager.o
"_OBJC_CLASS_$_TWCIncomingInvite", referenced from:
type metadata accessor for __ObjC.TWCIncomingInvite in TwilioManager.o
"_OBJC_CLASS_$_TWCLocalMedia", referenced from:
type metadata accessor for __ObjC.TWCLocalMedia in TwilioManager.o
"_OBJC_CLASS_$_TWCOutgoingInvite", referenced from:
type metadata accessor for __ObjC.TWCOutgoingInvite in TwilioManager.o
"_OBJC_CLASS_$_TwilioAccessManager", referenced from:
type metadata accessor for __ObjC.TwilioAccessManager in TwilioManager.o
"_OBJC_CLASS_$_TwilioConversationsClient", referenced from:
type metadata accessor for __ObjC.TwilioConversationsClient in TwilioManager.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
的Scala DSL中，有很多方法可以识别select：
Column 'name或$"name" col(name) 要从expr("nvl(name, 'unknown') as renamed")获得TypedColumn，您只需使用Column。
例如：myCol.as[T]