Slick lifted update on an Object

Question

I do updates on lifted entities using Slick. This code updates the firstName of a Contact object:

def updateContact(id: Int, firstName: Option[String]): Unit = {
  val q1 = for {
    c <- Contacts
    if c.id is id
  } yield c.firstName
  // Update value with same or new value
  q1.update(firstName.getOrElse(q1.list().head))
}

The option here is already useful for updating the value in case it is a Some (although it would be nicer if the update only happened if there is a new value).

What I am looking for is a way to query the object by ID, then do all the updates in memory using getOrElse and then do an update on the whole object.

Else I have to run the above for each field of the object which works but you know, feels like a dirty hack.

Answer 1

Instead of q1.update(firstName.getOrElse(q1.list().head)) you can write firstName.foreach{ fn => q1.update(fn) } which is shorter, simpler, one instead of two queries :). Using foreach on Option stops looking weird when you think of it as a collection with one or zero elements.

Regarding your idea to fetch the whole object, modify it and save it back, you can do it like this:

def updateContact(id: Int, firstName: Option[String], lastName:Option[String], ...): Unit = {
  val q1 = Query(Contacts).filter(_.id === id)
  val c = q1.first
  val modifiedC = c.copy(
    firstName = firstName.getOrElse(c.firstName),
    lastName = lastName.getOrElse(c.lastName),
    ...
  )
  q1.update(modifiedC)
}

Here is another example: http://sysgears.com/notes/how-to-update-entire-database-record-using-slick/

This is clean and simple and probably the best way to do it if performance is not mission critical as this always transfers all columns of Contacts . You can save some traffic by only transferring selected columns.