How to share models between frontend and backend

[marcvk]

Hi,

I'm struggling to find a good solution to share the models between my frontend (outwatch using scalajs) and my backend (play framework 3.0.5) using (of course) scalasql (version 0.1.11).

The problem is that I can't use the scalasql import in my frontend code, so I can't define the case class and object in the shared module.

I've now just duplicated the models in my frontend src tree and backend src tree.

I don't see an obvious way to avoid duplication, has anyone found a proper solution for this?

Kind regards,
Marc.

[marcvk]

Ok, with the help of a little AI, I've figured out that you can in fact have a JVM and a JS part in the shared section, so building on that I managed to solve it.

If anyone has other suggestions for different solutions or improvements to the solution below, they would still be welcome.

Here is what I did:

I've got a server, client and shared project in my build.sbt:

lazy val server = (project in file("server"))
  .settings(commonSettings)
  ... etc.

lazy val client = (project in file("client"))
  .settings(commonSettings)
  ... etc.

lazy val shared = crossProject(JSPlatform, JVMPlatform)
  .crossType(CrossType.Full)
  .in(file("shared"))
  .settings(commonSettings)
  .settings(
    libraryDependencies ++= Seq(
      "com.typesafe.play" %%% "play-json" % playJsonVersion,
      "com.lihaoyi" %%% "upickle" % "4.0.0"
    )
  )
  .jvmSettings(
    libraryDependencies ++= Seq(
      "com.lihaoyi" %% "scalasql" % scalasqlVersion
    )
  )
  .jsConfigure(_.enablePlugins(ScalaJSWeb))

So the key here is to use:

1. CrossType.Full (instead of Pure which is what I had initially)
2. put the dependency for scalasql in the .jvmSettings on the shared project (instead of in the server)
3. the directory tree layout for CrossType.Full is a little different:

   shared/
     shared/
       src/
     js/
       src/
     jvm/ 
       src/
   

4. Define the models in shared/src/main/.../ in the usual way, but have a different implementation of Table for the jvm and the js source:
   1. js/src/main/.../models/Table.scala:

        trait Table[T[_[_]]]

   2. jvm/src/main/.../models/Table.scala:

        import scalasql.{Table => SqlTable}
        type Table[T[_[_]]] = SqlTable[T]

[aboisvert]

One thing I would try is to have only the data objects (the "row" case classes) in the shared project, and keep the tables in the server/jvm project.

[marcvk]

but are they not companion objects? And should they therefore not be in the same file?