In the previous unit, you learned about collections and error handling. In this lesson, you’ll discover a feature of the Scala language called implicit. It is one of its most controversial traits. On one hand, it allows you to write less code and express extremely powerful abstractions. On the other hand, it can make your program more difficult to understand, and it increases its compilation time if misused. In this lesson, rather than introducing you to all the uses implicits have, you’ll focus on its primary usage. Implicits also have a slightly different syntax between Scala 2 and Scala 3, but their core principles remain the same. You’ll define a function that takes implicit parameters and mark a value as implicit in Scala 2 or as using in Scala 3. You’ll learn how the compiler searches for a match for an implicit parameter, which is a process called implicit resolution. You’ll also see how to express ad hoc polymorphism using a pattern called type class using the keywords implicit in Scala 2 and given . . . with in Scala 3. In the capstone, you will use implicits to define the number of threads to use when reading and writing the questions and answers to the database for your quiz application.
