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

## Define symbols
Symbols are similar to strings. **Symbols** are instances of the `Symbol` class,  just as strings are instances of the `String` class). Here is how we can define a symbol in Ruby:

```ruby
# assign symbol :something to variable "x"
x = :something
```

Compare the code above to the string’s definition:

```ruby
x = "something"
x = 'something' # alternative syntax
```

## Uses of symbols
We use symbols when, logically, a variable belongs to a set of similar values, for example:

```ruby
order.status = :confirmed
order.status = :cancelled
``` 

The `:confirmed` symbol can be used in other parts of a program. But why are we using symbols in Ruby when the code above works well with strings? Consider:

```ruby
order.status = 'confirmed'
order.status = 'cancelled'
```
It’s true. We often don’t have to use symbols. In some programming languages, there is no concept of symbols. However, there are a few reasons why a Ruby programmer may want to use symbols.

The first reason is that symbols are immutable. We can’t perform dangerous operations on them, but it’s possible to perform such operations on strings, like `upcase!`. In other words, by using symbols, we demonstrate our intent: This value is fixed, and there is probably a limited set of similar values.


It’s similar to a theatre ticket. We can write “Sectio A” by hand on every ticket, or we can use a rubber stamp for this purpose. Stamping takes fewer resources and is much faster. Moreover, every word written by hand is unique, like strings. They may look the same, but they are located in different computer memory parts. Conversely, stamped words are always the same and lead to only one source.

The second reason is that symbols are efficient and reusable and, because of immutability, the Ruby interpreter doesn’t need to allocate memory every time we create a new symbol. For example, if we have a string of `something`, which is nine characters, and we define this string in thousands of different places, the interpreter will use at least 9,000 bytes of memory when the program gets executed.


But that’s not the case with symbols. We allocate only one chunk of memory per symbol, so no matter how many definitions of `something` we have, we use only nine bytes of memory.

Technically speaking, references to the same symbols are always the same. References to the same strings aren’t always the same, but they can be the same.

Let’s  try a tricky way to create an array of strings. For each create operation, we’ll be calling a block:

```ruby
arr = Array.new(100) { 'something' } 
```

The code given above creates 100 strings of `something`. These strings are all different objects. Here is how we can verify that using the `__id__` property of each object:

```ruby
> arr[0].__id__
70100682145140
> arr[1].__id__
70100682144840
```
But when we create an array of symbols using the same trick, the result is different. The object identifier is always the same:

```ruby
$ pry
> arr = Array.new(100) { :something }
...
> arr[0].__id__
2893788
> arr[1].__id__
2893788
```

In other words, an array of symbols has references to only one object.


Another benefit of symbols is that Ruby compares symbols by reference only. Reference is just a value like `0xDEADBEEF` that fits into one of the CPU registers (4-8 bytes, depending on the architecture).
> Try the commands given above in the terminal below.


# Define symbols
Symbols are similar to strings. **Symbols** are instances of the `Symbol` class,  just as strings are instances of the `String` class). Here is how we can define a symbol in Ruby:

```ruby
# assign symbol :something to variable "x"
x = :something
```

Compare the code above to the string’s definition:

```ruby
x = "something"
x = 'something' # alternative syntax
```

# Uses of symbols
We use symbols when, logically, a variable belongs to a set of similar values, for example:

```ruby
order.status = :confirmed
order.status = :cancelled
``` 

The `:confirmed` symbol can be used in other parts of a program. But why are we using symbols in Ruby when the code above works well with strings? Consider:

```ruby
order.status = 'confirmed'
order.status = 'cancelled'
```
It’s true. We often don’t have to use symbols. In some programming languages, there is no concept of symbols. However, there are a few reasons why a Ruby programmer may want to use symbols.

The first reason is that symbols are immutable. We can’t perform dangerous operations on them, but it’s possible to perform such operations on strings, like `upcase!`. In other words, by using symbols, we demonstrate our intent: This value is fixed, and there is probably a limited set of similar values.


It’s similar to a theatre ticket. We can write “Sectio A” by hand on every ticket, or we can use a rubber stamp for this purpose. Stamping takes fewer resources and is much faster. Moreover, every word written by hand is unique, like strings. They may look the same, but they are located in different computer memory parts. Conversely, stamped words are always the same and lead to only one source.

The second reason is that symbols are efficient and reusable and, because of immutability, the Ruby interpreter doesn’t need to allocate memory every time we create a new symbol. For example, if we have a string of `something`, which is nine characters, and we define this string in thousands of different places, the interpreter will use at least 9,000 bytes of memory when the program gets executed.


But that’s not the case with symbols. We allocate only one chunk of memory per symbol, so no matter how many definitions of `something` we have, we use only nine bytes of memory.

Technically speaking, references to the same symbols are always the same. References to the same strings aren’t always the same, but they can be the same.

Let’s  try a tricky way to create an array of strings. For each create operation, we’ll be calling a block:

```ruby
arr = Array.new(100) { 'something' } 
```

The code given above creates 100 strings of `something`. These strings are all different objects. Here is how we can verify that using the `__id__` property of each object:

```ruby
> arr[0].__id__
70100682145140
> arr[1].__id__
70100682144840
```
But when we create an array of symbols using the same trick, the result is different. The object identifier is always the same:

```ruby
$ pry
> arr = Array.new(100) { :something }
...
> arr[0].__id__
2893788
> arr[1].__id__
2893788
```

In other words, an array of symbols has references to only one object.


Another benefit of symbols is that Ruby compares symbols by reference only. Reference is just a value like `0xDEADBEEF` that fits into one of the CPU registers (4-8 bytes, depending on the architecture).
> Try the commands given above in the terminal below.


Learn what symbols are and how to use them in Ruby.


Symbols

Learn what symbols are and how to use them in Ruby.

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

Symbols

Define symbols

Uses of symbols