We'll start with the Factory Method formalized in the book Design Patterns by Gang of Four.
This is one of the first patterns I teach my students. They're usually very anxious about the whole concept of design patterns, since it has an aura of mystery and complexity. So, what I do is ask them the following question.
Assume you have some class declaration, for example:
class Cat { val name = "Cat"}
Could you write a function that returns a new instance of the class? Most of them would succeed:
fun catFactory() : Cat { return Cat()}
Check that everything works:
val c = catFactory() println(c.name) // Indeed prints "Cat"
Well, that's really simple, right?
Now, based on the argument we provide it, can this method create one of two objects? ...
