Become a Ruby Professional

This module provides a thorough explanation of modern concepts for beginners. 
Beginners will get a refresher on Ruby. Those who’re already familiar with the language will rediscover object-oriented concepts, memory organization, find career advice, and save the planet from a nuclear apocalypse.
Let's tune in!

The Handbook for Ruby Developers

Key-value storage with a database backend.

Data remains in the hash and can be reused.

Everything disappears, and the hash will be empty.

When the program ends, what happens with the keys and values of a Ruby hash on the next run?

When the program ends, what happens with the keys and values of a Ruby hash on the next run?

A mix of hashes, arrays, and simple types, and can be used in Ruby.

A mix of hashes, arrays, and simple types and cannot be used in Ruby.

JavaScript Object Notation, and there is no JSON support in Ruby. 

What is the result of the following expression?
```ruby
dict = {
  'hello' => 'привет',
  'Vladimir' => 'Володя',
  'bye' => 'пока',
  'Sarah' => 'Сара'  
}
dict['hello'] + ', ' + dict['Vladimir']

What is the result of the following expression?
<pre><code class="language-ruby">dict = {
 'hello' =&gt; 'привет',
 'Vladimir' =&gt; 'Володя',
 'bye' =&gt; 'пока',
 'Sarah' =&gt; 'Сара' 
}
dict['hello'] + ', ' + dict['Vladimir']</code></pre>

On average, a hash data structure has _____ lookup complexity


On average, a hash data structure has _____ lookup complexity

An array has _____ lookup complexity.

What is the result of the following expression?
```ruby
hh = {}
hh['sam'] = 'math';
hh['pat'] = 'arts';
hh[:pat]

What is the result of the following expression?
<pre><code class="language-ruby">hh = {}
hh['sam'] = 'math';
hh['pat'] = 'arts';
hh[:pat]</code></pre>

What is the result of the following expression?
```ruby
hh = Hash.new(0)
hh['sam'] = 'math';
hh['pat'] = 'arts';
hh[:pat]

What is the result of the following expression?
<pre><code class="language-ruby">hh = Hash.new(0)
hh['sam'] = 'math';
hh['pat'] = 'arts';
hh[:pat]</code></pre>

What is the result of the following expression?
```ruby
def calc(a, b)
  a ** b
end

calc(2, 8)

What is the result of the following expression?
<pre><code class="language-ruby">def calc(a, b)
 a ** b
end

calc(2, 8)</code></pre>

**True or False:** We should prefer a hash set over a regular hash when there is no need for keeping values in a hash, and you have only keys to add.


True or False: We should prefer a hash set over a regular hash when there is no need for keeping values in a hash, and you have only keys to add.

What is the result of the following expression?
```ruby
users = [
  {
    address1: {
      street1: '123 Market street',
      street2: 'apt 504'
    }
  },
  {
    address2: {
      street1: '555 El Camino',
      street2: 'unit 5'
    }
  },
]

users[1].dig(:address2, :street2)

What is the result of the following expression?
<pre><code class="language-ruby">users = [
 {
 address1: {
 street1: '123 Market street',
 street2: 'apt 504'
 }
 },
 {
 address2: {
 street1: '555 El Camino',
 street2: 'unit 5'
 }
 },
]

users[1].dig(:address2, :street2)</code></pre>

What is the result of the following expression?
```ruby
hh = { admin: false, login: 'pat', password: '123456' }
hh.has_key?(:admin)

What is the result of the following expression?
<pre><code class="language-ruby">hh = { admin: false, login: 'pat', password: '123456' }
hh.has_key?(:admin)</code></pre>

Take a quiz on hashes before moving on to the next chapter.


Quiz: Hashes

Take a quiz on hashes before moving on to the next chapter.

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

Appendix

Conclusion

Quiz: Hashes