Explore OOP in Ruby to gain a deeper understanding of Ruby objects, Ruby methods, and Ruby classes, enabling you to solve multiple problem sets with an object-oriented approach.

Become a Ruby Developer

Module Overview
Ruby is a smart, functional, and object-oriented programming language that blends the best features of scripting power with user-friendly syntax. In this module, we’ll dive into OOP in Ruby with hands-on practice using interactive exercises and illustrations. We'll start by creating and managing Ruby objects. Next, we’ll explore Ruby methods and blocks, essential tools in Ruby programming. Finally, we'll delve into Ruby classes and how they are used to implement OOP principles.

Ruby OOP (Object-Oriented Programming)

Now is a good time to explore the concepts of nothingness and truth in Ruby. First, let’s also do a quick recap to build some context.

## The `nil` object

We’ve briefly mentioned that in Ruby, there’s an object that represents nothing, `nil`.

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


dictionary = { :one => "eins", :two => "zwei", :three => "drei" }
p dictionary[:one]

This prints out `"eins"`. However, what happens if we try to receive the value for a key that hasn’t been defined on the hash?

dictionary = { :one => "eins", :two => "zwei", :three => "drei" }
p dictionary[:four]

This prints out `nil`. Remember that every method call always returns some value. In cases where there’s nothing to return, it returns `nil`, which represents nothing.

Note that `nil` isn’t `0`, which represents something. An empty string (`""`), an empty array (`[]`), or an empty hash (`{}`) also all represent something. So, they’re not `nil`.

## The `true` and `false` objects

We’ve also discussed that in order to represent truth and the opposite of it, Ruby also knows the values `true` and `false`.

We’ve seen them as returned values when we tried some of the methods on numbers, strings, and arrays, like `3.odd?`, `"a string".start_with?("a")`, or `[1, 2, 3].include?(2)`.

These so-called predicate methods always return either `true` or `false`.

> **Remember:** Predicate methods end with a question mark and return `true` or `false`.

## They have classes

The `nil`, `true`, and `false` objects also have classes, and we can verify that: `nil.class`, `true.class` and `false.class`.

## Truthiness and falsiness

When we discussed `if` statements, we used methods that actually return `true` and `false` values, like the `odd?` method on numbers do. Comparison operators like `==`, `<`, and `>` also return `true` and `false`, as in:

Now is a good time to explore the concepts of nothingness and truth in Ruby. First, let’s also do a quick recap to build some context.

# The `nil` object

We’ve briefly mentioned that in Ruby, there’s an object that represents nothing, `nil`.

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


This prints out `nil`. Remember that every method call always returns some value. In cases where there’s nothing to return, it returns `nil`, which represents nothing.

Note that `nil` isn’t `0`, which represents something. An empty string (`""`), an empty array (`[]`), or an empty hash (`{}`) also all represent something. So, they’re not `nil`.

# The `true` and `false` objects

We’ve also discussed that in order to represent truth and the opposite of it, Ruby also knows the values `true` and `false`.

We’ve seen them as returned values when we tried some of the methods on numbers, strings, and arrays, like `3.odd?`, `"a string".start_with?("a")`, or `[1, 2, 3].include?(2)`.

These so-called predicate methods always return either `true` or `false`.

> **Remember:** Predicate methods end with a question mark and return `true` or `false`.

# They have classes

The `nil`, `true`, and `false` objects also have classes, and we can verify that: `nil.class`, `true.class` and `false.class`.

# Truthiness and falsiness

When we discussed `if` statements, we used methods that actually return `true` and `false` values, like the `odd?` method on numbers do. Comparison operators like `==`, `<`, and `>` also return `true` and `false`, as in:

Learn about truthiness, falsiness, and nothingness.

Objects

Blocks

Conditionals

Writing Classes

Mini project 1

Conclusion

Nothingness and the Truth

The `nil` object