Nothingness and the Truth

Now is a good time to talk about the concepts of nothingness and truth in Ruby.

Nil

We have briefly mentioned that in Ruby there is an object that represents "nothing": the object nil.

That’s right. “Nothing” is a thing in Ruby (as well as in many other languages), albeit a very special one. We could ramble on the philosophical implications of this, but instead we’ll just look at how this is used in practice:

Remember how we can receive a value associated with a key from a hash?

This will print out "eins". However, what happens if we try to receive the value for a key that has not been defined on the hash?

This will print out nil. Remember that every method call always will return some value? In cases where there’s nothing to return, it will return nil, which represents nothing :)

In Ruby, nil, nothing, is something else than, for example, 0, which represents something. An empty string "", an empty array [], or empty Hash {} also all represent something. So they’re not nil. ...