Private classes in Ruby
One of the most common way to make some part of your code more understandable and explicit is to extract a class. However, many times this class is not intended for public usage. It’s an implementation detail of a bigger unit. It should not be used be anyone else but the module in which it is defined.
So how do we hide such class so that others are not tempted to use it? So that it is clear that it is an implementation detail?
I recently noticed that many people don’t know that since Ruby 1.9.3 you can make a constant private. And that’s your answer to how.
class Person class Secret def to_s "1234vW74X&" end end private_constant :Secret def show_secret Secret.new.to_s end end
Person class can use
Person.new.show_secret # => 1234vW74X&
But others cannot access it.
Person::Secret.new.to_s # NameError: private constant Person::Secret referenced
Person is the public API that you expose to other parts of the system and
Person::Secret is just an
You should probably not test
Person::Secret directly as well but rather through the public
that your clients are going to use. That way your tests won’t be brittle and depended on implementation.
That’s it. That’s the entire, small lesson. If you want more, subscribe to our mailing list below or buy Fearless Refactoring.