Using .tupled method when companion object is in c

问题:

I am in the process of migrating from Slick to Slick 2, and in Slick 2 you are meant to use the tupled method when projecting onto a case class (as shown here http://slick.typesafe.com/doc/2.0.0-RC1/migration.html)

The problem is when the case class has a companion object, i.e. if you have something like this

case class Person(firstName:String,lastName:String) {

}

Along with a companion object

object Person {
  def something = "rawr"
}

In the same scope, the tupled method no longer works, because its trying to run tupled on the object, instead of the case class.

Is there a way to retrieve the case class of Person rather than the object, so you can call tupled properly?

回答1:

You can also write

(Person.apply _).tupled

to avoid repeating the types.

回答2:

This is very similar to what Alexey Romanov said, but in order to avoid lifting apply whenever you need tupled, we just add it to our companion objects.

object Person {
  def something = "rawr"
  def tupled = (Person.apply _).tupled
}

Now you can call Person.tupled just like you would have if it didn't have a companion object.

回答3:

One workaround is define a companion object as follows:

object Person extends((String,String) => Person) {
    ...
}

See. https://groups.google.com/d/msg/scala-user/jyWBMz5Qslw/Bryv4ftzRLgJ

回答4:

To build on some of the other comments you could do the following as well since tuple is calling the generated default apply method for the case class.

object Person {
  ...
  def tupled = (this.apply _).tupled
}