Recently, Daniel Westheide wrote an interesting post about the abuse of the Option type in Scala. You can find it here. I couldn’t agree more with Daniel. This short story is another example that demonstrates how using Option is not always the best option (pun intended). I’m developing an advertising service for a customer using Scala. A simplified version of the Ad data structure is the following: final case class Ad( headline: String, description1: String, description2: String ) At some point they told me we need to support, by adding the headline2 field, two types of ad: standard and expanded.
Yesterday my mate asked me: “I have a List[String] and a Map[String, Int] and I want a List[Int] where its values are those of the Map whose keys match the List[String] elements, maintaining the order. Should I use pattern matching?“. I know, the sentence is a bit convoluted but the code will make it clear, hopefully. Anyway, I replied: “No, you don’t need pattern matching, you just need this”:
For this post I’ll consider the following simple case class unless otherwise specified: case class Person(lastname: String, firstname: String, birthYear: Int) In this post: Common knowledge about case classes Not so common knowledge about case classes Defining a case class using the curried form Defining a case class with a private constructor For the most curious ones Final Notes Common knowledge about case classes When you declare a case class the Scala compiler does the following for you: