Why do I get "expected class or object definition" when defining a type in scala?

scala slick
gotch4 picture gotch4 · Mar 13, 2015 · Viewed 8.2k times · Source

If I write something like this (to define Slick tables as per docs):

type UserIdentity = (String, String)
class UserIdentity(tag: Tag){
...
}

I get a compile error: "expected class or object definition" pointing to the type declaration. Why?

Answer

Dan Simon picture Dan Simon · Mar 13, 2015

You can't define type aliases outside of a class, trait, or object definition.

If you want a type alias available at the package level (so you don't have to explicitly import it), the easiest way around this to define a package object, which has the same name as a package and allows you to define anything inside of it, including type aliases.

So if you have a foo.barpackage and you wish to add a type alias, do this:

package foo

package object bar {
  type UserIdentity = (String, String)
}

//in another file
package foo.bar
val x: UserIdentity = ...

Related questions

Slick 3.0 Insert and then get Auto Increment Value

I have written this code which works perfectly class Items(tag: Tag) extends Table[Item](tag, "ITEMS") { def id = column[Long]("ITEMS_ID", O.PrimaryKey, O.AutoInc) def name = column[String]("ITEMS_NAME") def price = column[Double]("ITEMS_PRICE") def * = (…

Read More
View SQL query in Slick

Is there a way to observe an SQL statement that will be generated by Query? For example, I have this: val q = actions.filter(v => v.actionHash === hash && v.carriedAt > past) Can I view its underlying …

Read More
Logging options for Slick

I'm createing a Play 2.1 app, in which I have decided to use Slick for database interaction. However I can't find documentation about how to configure/enable logging for Slick. Anyone knows this?

Read More