Autoinsert UUID on object creation

[Alexander Zafirov]

I have an object with a field that's of type UUID:

def uuid = column[UUID]("uuid", O.PrimaryKey)

I would like hide from the client the possibility to enter uuids but rather provide them when the object is instantiated. I figured that I need to have a

case class Foo private(uuid, ...)

and then create a companion object with an apply method that would generate UUID.randomUUID().

The problem is that once I create the apply method I get two errors:

- "method unapply is defined twice"

- "ambiguous reference to overloaded definition, both method apply [...] match expected type ?"

I found this but it wasn't very useful. 

Any help would be appreciated,

Alex

[Mirco Dotta]

This is a known limitation of case classes in Scala. You can work around it by declaring the case class abstract.

Cheers,

Mirco

----------------

Mirco Dotta - @mircodotta

Typesafe – Build reactive apps!

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[Alexander Zafirov]

Hi Mirco,

Can you please elaborate a bit more on how I instantiate the case class in the apply method of the companion object once it is declared as abstract?

Best,

Alex

[Mirco Dotta]

Hi Alex, sure thing. Here you go

abstract case class A private(a: Int)

object A {

  def apply(): A = new A(2){}

}

----------------

Mirco Dotta - @mircodotta

Typesafe – Build reactive apps!

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/80ab90b1-1bcd-4954-bd06-179f9481a54b%40googlegroups.com.

[Alexander Zafirov]

Hi Mirco,

And what about the mapping of the class?

For example how do I resolve this case:

abstract case class User(foo: Int, name: String, id: Option[Int] = None)

object User {

  def apply(name: String): User = new User(1, name){}

}

class Users(tag: Tag) extends Table[User](tag, "USERS") {

  // Auto Increment the id primary key column

  def id = column[Int]("ID", O.PrimaryKey, O.AutoInc)

  // The name can't be null

  def name = column[String]("NAME")

  // the * projection (e.g. select * ...) auto-transforms the tupled

  // column values to / from a User

  def * = (name, id.?) <> (User.apply, User.unapply)

}

This gives me 

Error:(58, 33) type mismatch;

 found   : String => User

 required: ((Int, String, Option[Int])) => User

  def * = (name, id.?) <> (User.apply, User.unapply)

                                ^

and 

Error:(58, 24) No matching Shape found.

Slick does not know how to map the given types.

Possible causes: T in Table[T] does not match your * projection. Or you use an unsupported type in a Query (e.g. scala List).

  Required level: slick.lifted.FlatShapeLevel

     Source type: (slick.lifted.Rep[String], slick.lifted.Rep[Option[Int]])

   Unpacked type: (Int, String, Option[Int])

     Packed type: Any

  def * = (name, id.?) <> (User.apply, User.unapply)

                       ^

[Mirco Dotta]

I think you’ll have to write a mapping function. See http://slick.typesafe.com/doc/3.0.0/schemas.html#mapped-tables for some context.

----------------

Mirco Dotta - @mircodotta

Typesafe – Build reactive apps!

To view this discussion on the web visit https://groups.google.com/d/msgid/scalaquery/0f2390eb-069b-4f19-be81-35b0b93cc876%40googlegroups.com.