Play Slick handling Date with matching Shapes and Implicits - scala

Question

I am adding two additional fields to the Person table: a Date and a String. I built the Person tabel and mapped it with Play Slick by following olivebh's tutorial.
However, I get the following erros from the Slick data model trait Tables:
dao/Tables.scala:85: ambiguous implicit values:
[error] both value e3 of type slick.jdbc.GetResult[String]
[error] and value e1 of type slick.jdbc.GetResult[String]
[error] match expected type slick.jdbc.GetResult[String]
[error] ProjectRow.tupled((<<[Int], <<[String], <<[Date], <<[String]))
which refers to the following line:
implicit def GetResultPersonRow(implicit e0: GR[Int], e1: GR[String], e2: GR[Date], e3: GR[String]): GR[ProjectRow] = GR {
prs =>
import prs._
PersonRow.tupled((<<[Int], <<[String], <<[Date], <<[String]))
}
where the "int, string, date, string" represent the "id, name, birthdate, language" fields respectively. Everything worked fine by following the tutorial that covers "id, name" as an example. But as soon as I added birthdate and language, I got the error quoted above.
Also, when creating the prototypes for the table rows:
class Person(_tableTag: Tag) extends Table[PersonRow](_tableTag, "person") {
def * = (personId, name, birthdate, language) <>(PersonRow.tupled, PersonRow.unapply)
def ? = (Rep.Some(personId), Rep.Some(name), Rep.Some(birthdate), Rep.Some(language)).shaped.<>({ r => import r._; _1.map(_ => ProjectRow.tupled((_1.get, _2.get, _3.get, _4.get))) }, (_: Any) => throw new Exception("Inserting into ? projection not supported."))
val personId: Rep[Int] = column[Int]("person_id", O.AutoInc, O.PrimaryKey)
val name: Rep[String] = column[String]("name", O.Length(50, varying = true))
val birthdate: Rep[Date] = column[Date]("birthdate", O.Length(50, varying = true))
val language: Rep[String] = column[String]("language", O.Length(50, varying = true))
I get the following errors:
No matching Shape found.
[error] Slick does not know how to map the given types.
[error] Possible causes: T in Table[T] does not match your * projection. Or you use an unsupported type in a Query (e.g. scala List).
[error] Required level: slick.lifted.FlatShapeLevel
[error] Source type: (slick.lifted.Rep[Int], slick.lifted.Rep[String], slick.lifted.Rep[java.util.Date], slick.lifted.Rep[String])
[error] Unpacked type: (Int, String, java.util.Date, String)
[error] Packed type: Any
[error] def * = (personId, name, birthdate, language) <>(PersonRow.tupled, PersonRow.unapply)
and also:
dao/Tables.scala:94: could not find implicit value for parameter od: slick.lifted.OptionLift[Tables.this.driver.api.Rep[java.util.Date],O]
[error] def ? = (Rep.Some(personId), Rep.Some(name), Rep.Some(birthdate), Rep.Some(language)).shaped.<>({ r => import r._; _1.map(_ => PersonRow.tupled((_1.get, _2.get, _3.get, _4.get))) }, (_: Any) => throw new Exception("Inserting into ? projection not supported."))
dao/Tables.scala:94: not found: value _1
[error] def ? = (Rep.Some(personId), Rep.Some(name), Rep.Some(birthdate), Rep.Some(language)).shaped.<>({ r => import r._; _1.map(_ => PersonRow.tupled((_1.get, _2.get, _3.get, _4.get))) }, (_: Any) => throw new Exception("Inserting into ? projection not supported."))
Any help in understanding these errors and therefore how I could change the Slick data model trait in order for it to properly handle two additional Date and String fields, would be greatly appreciated. Thank you so much!

Answer 1

Slick can't handle java.util.Date because databases understand only java.sql.Date via JDBC drivers. You can make your own mapper, so that Slick can know how to read/write java.util.Date/java.sql.Date. But, Java 8 now has a better API for handling date/time/calendars.
implicit val localDateTimeColumnType = MappedColumnType.base[LocalDateTime, Timestamp](
ldt => Timestamp.valueOf(ldt),
t => t.toLocalDateTime
)
See this question also. Btw, thanks for reading my article, hope it was useful! :)