This presentation provides an overview on Value Classes in Scala, which is explained in the video on the last slide by Alejandro Lujan. He explains why you would want to use them, outlines the restrictions that are associated with them, and shows examples of how you would use them. Value classes are a mechanism that Scala provides to create a certain type of wrapper classes that provide memory and performance optimizations. In this video, we show a use case for Tiny Types with Value classes.

1. Value classes

4. WHY?
• Performance optimizations
– Fewer instances => no initialization time
• Memory optimizations
– Fewer instances => less memory usage

5. Restrictions
• One class parameter
• Must be the only immutable field

6. How
case class UserId(id: Int)
extends AnyVal

7. Use case: tiny types
case class User (id: Int, name: String)
case class Tweet(id: Int, content: String)

8. case class User (id: Int, name: String)
case class Tweet(id: Int, content: String)
object Test {
val user = User(5, "Groot")
val tweet = Tweet(42, "I am Groot")
println("User id: " + user.id)
println("Tweeted " + tweet.content)
}

9. case class UserId(id: Int)
case class UserName(name: String)
case class TweetId(id: Int)
case class TweetContent(content: String)
case class User(id: UserId, name: UserName)
case class Tweet(id: TweetId,
content: TweetContent)

10. object Test {
val user = User(UserId(5),
UserName("Groot"))
val tweet = Tweet(TweetId(42),
TweetContent("I am Groot"))
println("User id: " + user.id)
println("Tweeted " + tweet.content)
}

11. > :javap –p User
public class User … {
private final UserId id;
private final UserName name;
…
}

12. case class UserId(id: Int)
extends AnyVal
case class UserName(name: String)
extends AnyVal
case class TweetId(id: Int)
extends AnyVal
case class TweetContent(content: String)
extends AnyVal
case class User(id: UserId, name: UserName)
case class Tweet(id: TweetId, content: TweetContent)

13. > :javap –p User
public class User … {
private final int id;
private final java.lang.String name;
…
}