Gain insights into Ruby development with 78 tasks tailored for beginners and experienced coders. Explore object-oriented concepts, debug programs, and advance your freelance coding career.

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This self-study course written as a book is your first step towards making money by coding and programming from home, and having fun doing it. You will understand how the Ruby language works, and establish a foundation for being a successful freelance developer. This course gives you not only technical detail, but presents knowledge in a friendly format, understandable by all ages, providing a thorough explanation of modern concepts for absolute beginners.

In this course you will find 78 easy to follow tasks, so even people without any programming skill can solve them. Beginners will learn how to create, debug, and understand programs in Ruby. Those who are already familiar with the language will rediscover object-oriented concepts, memory organization, find career advice, and save the planet from a nuclear apocalypse.

Ready to dive into one of the most influential and demanding third generation programming languages? Let's tune in!

The Handbook for Ruby Developers

# Defining hash in Ruby
To define a hash in a Ruby program, we need to use curly brackets. Remember that we use square brackets for arrays:


```
$ pry
> obj = {}
...
> obj.class
Hash < Object
```

We should not name the variable `hash` because it is a reserved language keyword, but we can enter it into the REPL and see what happens. That’s why the authors usually use `obj` (object) or`hh`(double “h” indicates it’s more than just a variable).

Programmers say that the hash is **key-value storage**, where each key is assigned a value. For example, the key is `ball`, a string, and the value is the physical object `ball` itself. The hash is often called a **dictionary**. This is partly true because the dictionary of words is a perfect example of hash. Each key, or word, has a meaning, or a description of the word or a translation. In Java, language hash used to be called a dictionary too, but since the seventh version, this concept has become obsolete, and the dictionary has been renamed to **map**.

The key and value in the hash can be any object, but most often, the key is a string or symbol, and the value is the actual object. It is difficult to predict what it will be. It can be a string, a symbol, an array, a number, another hash. So when developers define a hash in a Ruby program, they usually know in advance what type it will keep.

For example, let’s agree that the key in the hash is a symbol, and the value is a number, type integer. We’ll keep the weight of different types of balls in grams inside of our hash:


```
obj = {}
obj[:soccer_ball] = 410
obj[:tennis_ball] = 58
obj[:golf_ball] = 45 
```

If we write this program into the REPL and type `obj`, we will see the following:

```
{
    :soccer_ball => 410,
    :tennis_ball => 58,
      :golf_ball => 45
}
```

The text above is perfectly valid from Ruby’s language perspective, and we could initialize our hash without writing the values and without using assignment operator `=`:

```
obj = {
    :soccer_ball => 410,
    :tennis_ball => 58,
      :golf_ball => 45
}
```

The operator `=>` in Ruby is called a **hash rocket**. In JavaScript, it’s known as  “fat arrow,” but has a different meaning. However, the hash rocket notation is now obsolete. It would be more correct to write the program this way:

```
obj = {
  soccer_ball: 410,
  tennis_ball: 58,
  golf_ball: 45
}
```

We should notice that even though the record looks different, we will get the same conclusion as above if we write `obj` in REPL. In other words, the keys, `:soccer_ball`, `:tennis_ball`, `:golf_ball`, are symbol types in this case.

To get the value back from the hash, use the following construction:


```ruby
puts 'Golf ball weight:'
puts obj[:golf_ball]
```

Learn how to use a hash in Ruby language.

Before We Begin

First Steps

Fundamentals of Ruby

Conditional Statements

Operators and Methods

Arrays

Hash

Fun with Object Oriented Programming

Debugging in Ruby

Ruby Version Manager

Testing Ruby Programs

Wrap Up!

Appendix

Hash in Ruby

Defining hash in Ruby