Foreign key relationship in Slick 2.1.0 and Traits - mysql

Question

So I have an existing project. I didn't write any of this, and the author's choice of how they implemented Slick confuses me somewhat.
Here is an existing table/slick set of classes:
case class SourcesRow(id: Long,
childSourceId: Long,
childSourceName: String,
parentSourceId: Long,
parentSourceName: String)
trait SourcesTable { this : DbProfile =>
import profile.simple._
class SourcesRows(tag : Tag) extends Table[SourcesRow](tag, "Sources") {
def id = column[Long]("Id", O.PrimaryKey, O.NotNull, O.AutoInc)
def childSourceId = column[Long]("ChildSourceId", O.NotNull)
def childSourceName = column[String]("ChildSourceName", O.NotNull)
def parentSourceId = column[Long]("ParentSourceId", O.NotNull)
def parentSourceName = column[String]("ParentSourceName", O.NotNull)
def * = (id, childSourceId, childSourceName, parentSourceId, parentSourceName) <> (SourcesRow.tupled, SourcesRow.unapply)
}
val sources = TableQuery[SourcesRows]
object SourcesTable {
def listSources()(implicit session: SessionDef) =
sources.run
}
}
...and we have several of them which are loaded into a database object like so
class ControlledValuesDb(override val profile: JdbcProfile) extends DbProfile
with RestrictionsTable
with RestrictionCategoriesTable
with SourcesTable
with CollectionsTable
with SiteDestinationsTable
with SupplementalCategoriesTable
with ListsTable
with ItemsTable {
...
}
Now I'm trying to add a table with a relationship (none of those tables have any relationships. I've been looking at the Slick 2.1 docs and it looks like I need to reference one TableQuery from the object, but I'm not quite sure how to accomplish that. See the ??? below:
case class ItemsRow(id: Long , listId: Long, value: String)
case class ListsRow(id: Long, name: String)
trait ListsTable { this: DbProfile =>
import profile.simple._
class ListsRows(tag: Tag) extends Table[ListsRow](tag, "Lists") {
def id = column[Long]("Id", O.PrimaryKey, O.NotNull, O.AutoInc)
def name = column[String]("Name", O.NotNull)
def * = (id, name) <> (ListsRow.tupled, ListsRow.unapply)
}
val lists = TableQuery[ListsRows]
object ListsTable {
}
}
trait ItemsTable { this: DbProfile =>
import profile.simple._
class ItemsRows(tag : Tag) extends Table[ItemsRow](tag, "Items") {
def id = column[Long]("Id", O.PrimaryKey, O.NotNull, O.AutoInc)
def listId = column[Long]("ListId", O.NotNull)
def value = column[String]("Val", O.NotNull)
//def list = foreignKey("fk_item_list_id", listId, ???)(_.id)
def * = (id, listId, value) <> (ItemsRow.tupled, ItemsRow.unapply)
}
val items = TableQuery[ItemsRows]
object ItemsTable {
}
}

Answer 1

If what you want is to have a table with relationship
You can model as follow
class PostTable(tag: Tag) extends Table[BlogPost](tag, "posts") {
def pid = column[Long]("pid", O.PrimaryKey, O.AutoInc)
def author = column[String]("author") // fk of user table
def userFK =
foreignKey("author_fk", author, TableQuery[UserTable])(_.email, ForeignKeyAction.Restrict, ForeignKeyAction.Cascade)
def * = (pid, author, title, content, postAt, tags) <> (BlogPost.tupled, BlogPost.unapply)
}
class UserTable(tag: Tag) extends Table[User](tag, "users") {
def email = column[String]("email", O.PrimaryKey)
def * = (email, password, name) <> (User.tupled, User.unapply)
}
Notice userFK in PostTable is a fk constraint
TableQuery is just an object that you can use to query your database
For example you have val sources = TableQuery[SourcesRows] in your code, which you can then do
sources.filter(_.pid === 1001L)
which means select * from Sources where pid = 1001;
Hope this help =)