The builder design pattern helps to create instances of classes using class methods rather than the class constructors. It is particularly useful in cases where a class might need multiple versions of its constructor in order to allow different usage scenarios. Moreover, in some cases, it might not even be possible to define all combinations or they might not be known. The builder design pattern uses an extra object, called builder, in order to receive and store initialization parameters before building the final version of an object.
In this subsection, we will provide a class diagram for the builder pattern the way it was classically defined and the way it looks in other languages, including Java. Later, we will present different versions of the code on the basis of them being more appropriate for Scala and of the observations and discussions we will have around them.
Let's have a Person class with different parameters: firstName, lastName, age, departmentId...