Traits extended by one-line case classes

Let's start talking about Scala, that pretty language making you able to use both object-oriented and functional programming paradigms.
If you've never heard about it, take a look at Scala School. You have to be at ease with trait and case class concepts to understand this post.

We all agree: keeping an abstract layer in your code is something good, but it's often painful when you have to rewrite n-times some children having a similar implementation.
I always try to keep that children readable and fast understandable by making them one-liners. Adding a child becomes quite easy, even for a non-scala developer.

Trivial trait

Let's define a trait that will be the minimal representation of a message.

trait Message {
  def id: String
  def content: String
}

case class DefaultMessage(id: String, content: String) extends Message
case class FromToMessage(id: String, content: String, from: String, to: String) extends Message

No need for writing overriding methods. Actually, id and content parameters are defined as methods that implicitly override Message's methods. Nice, isn't it?

Trait using serialization

OK, that was quite simple. But how will you do if you have to create custom serializer object for each message type? In that example, we will be using the lift framework to (de)serialize JSON.

trait MessageSerializer[M <: Message] {
  implicit val format = DefaultFormats

  def apply(m: M): String = {
    Serialization.write(m)
  }

  def unapply(s: String)(implicit mf: Manifest[M]): Option[M] = {
    for {
      jvalue <- JsonParser.parseOpt(s)
      m <- jvalue.extractOpt[M]
    } yield m
  }
}

object DefaultMessageSerializer extends MessageSerializer[DefaultMessage]
object FromToMessageSerializer extends MessageSerializer[FromToMessage]

If you don't know what are apply and unapply methods, just take a look at this sample code to understand their usage:

/* implicit call to apply method */
val a = DefaultMessage("1234", "Hello world!")
println(DefaultMessageSerializer(a)) // print: {"id": "1234", "content": "Hello world!"}

/* implicit call to unapply method */
"""{"id": "5678", "content": "Love", "from": "me", "to": "you"}""" match {
  case FromToMessageSerializer(m) => println(m) // print FromToMessage("5678", "Love", "me", "you")
  case _ => println("error")
}

Blog

À lire également

UP Programme: Who are the new winning startups?

Clever Cloud is proud to announce the arrival of new start-ups for the second promotion…

Company

Quentin Adam joins Micode on the Underscore_ podcast

Quentin Adam, CEO of Clever Cloud, was a guest on Underscore_, the tech podcast hosted by well-known French content creator Micode.
Company

PostgreSQL 16 and 17 available on Clever Cloud, migrate effortlessly

After upgrading our infrastructure and working hard over the last year to improve the quality of our service and accelerate new product releases, we're delighted to announce the availability of PostgreSQL 16 and 17 on Clever Cloud.
Engineering