TypedPipe can't coerce strings to DateTime even when given implicit function - scala

Question

I've got a Scalding data flow that starts with a bunch of Pipe separated value files. The first column is a DateTime in a slightly non-standard format. I want to use the strongly typed TypedPipe API, so I've specified a tuple type and a case class to contain the data:
type Input = (DateTime, String, Double, Double, String)
case class LatLonRecord(date : DateTime, msidn : String, lat : Double, lon : Double, cellname : String)
however, Scalding doesn't know how to coerce a String into a DateTime, so I tried adding an implicit function to do the dirty work:
implicit def stringToDateTime(dateStr: String): DateTime =
DateTime.parse(dateStr, DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss.S"))
However, I still get a ClassCastException:
val lines: TypedPipe[Input] = TypedPipe.from(TypedPsv[Input](args("input")))
lines.map(x => x._1).dump
//cascading.flow.FlowException: local step failed at java.lang.Thread.run(Thread.java:745)
//Caused by: cascading.pipe.OperatorException: [FixedPathTypedDelimite...][com.twitter.scalding.RichPipe.eachTo(RichPipe.scala:509)] operator Each failed executing operation
//Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to org.joda.time.DateTime
What do I need to do to get Scalding to call my conversion function?

Answer 1

So I ended up doing this:
case class LatLonRecord(date : DateTime, msisdn : String, lat : Double, lon : Double, cellname : String)
object dateparser {
val format = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss.S")
def parse(s : String) : DateTime = DateTime.parse(s,format);
}
//changed first column to a String, yuck
type Input = (String, String, Double, Double, String)
val lines: TypedPipe[Input] = TypedPipe.from( TypedPsv[Input]( args("input")) )
val recs = lines.map(v => LatLonRecord(dateparser.parse(v._1), v._2, v._3,v._4, v._5))
But I feel like its a sub-optimal solution. I welcome better answers from people who have been using Scala for more than, say, 1 week, like me.