This is the curriculum for the 2018 Foxtrot Web Developer Bootcamp.

Setting Up Ruby

Ruby is an open source, object-oriented programming language with a reputation for simplicity and a style that is both easy to read and write (no more curly braces!). If you are using a Mac, Ruby comes preinstalled on your machine. To use it, open the terminal and type irb into the window. And that's it! You're all set to start coding in Ruby.

If you're using Windows, go here: Windows Ruby Setup

Running Ruby from a File

Time to start running Ruby from a file.

To do this, create a file. Ruby can be run from a file with any sort of name, but it is common to give a ruby file a .rb extension. We've built up quite a few files with our Javascript work, so you might like to start putting your Ruby work in a new folder.

To run a file with Ruby code in it, you give the command ruby and then a path to the file (you'll need to be clear about how paths work; a quick google will get you thousands of explanations if you're still unclear). So to execute a ruby file called doit.rb in your current directory, you would do: ruby doit.rb

When ruby is running from the shell like this, you can read in a line from the user with the gets command.

x = gets
puts x.upcase

In the terminal run the file using ruby.

$ ruby uppercase-me.rb

The puts command is a little different from p: p is more for programmers to see inside the thing being displayed, while puts just writes the string out to the terminal (try changing the example to p).

Now you can make a program have a kind of dialog with the user.

puts "Enter your name"
name = gets
puts "Hello, #{name}. How are you today?"
wellness = gets
puts "Well, I hope you get over #{wellness} soon."

This doesn't quite work.

Enter your name
Hello, Guy
. How are you today?
Well, I hope you get over fine

The string we're getting from gets includes the return you type to end it. We can strip that off with chomp, which removes line endings from a string.

puts "Enter your name"
name = gets.chomp
puts "Hello, #{name}. How are you today?"
wellness = gets.chomp
puts "Well, I hope you get over #{wellness} soon."

You can also run a ruby file while in irb by using load, then in quotes the file name.

load './your_file.rb'


The IRB lines that prompt you with > are for new statements.

When the prompt says 1 or ? or " or 'instead, that means you are inside a method or string, and IRB is expecting you to finish entering your text and close your string or method with another quotation mark or end statement.

What you are doing is trying to enter your statement again, before you get a new (>) prompt.

If you are stuck in the middle of an incorrect statement and want to start over, press Ctrl-C and you will get a clean > prompt.

Ruby Style Guide

Correct styling conventions for Ruby made for code that is easy to read. You can find a maintained Ruby Styling Guide here: Ruby Styling Guide.


Rather than having to memorize all these conventions, you can use a tool based on this style guide called Rubocop. It will check your Ruby code for common styling errors. In order to install Rubocop, just type this into the terminal:

gem install rubocop

Checking your code against Rubocop is simple. If you type rubocop into the terminal, it will check any Ruby files found in your current directory against the style guide. If your Ruby files live in a different directory from where you're currently located in the terminal, simply give your file's path and name as an argument:

rubocop path/to/filename.rb

The output from rubocop may look something like:

Inspecting 1 file


myruby.rb:1:81: C: Line is too long. [131/80]
people = ['Joe', 'Mike, 'Sean', 'Liz', 'Fred', 'Alien'.reverse, 'Mary']
myruby.rb:9:5: C: Use snake_case for method names.
def createPair(people)

1 file inspected, 2 offenses detected

Please don't be offended at the language, rubocop is just doing it's job.

Ruby Basic Data Types



Integer operators and arithmetic in Ruby are very similar to what you've seen so far in Javascript:

> 1 + 3   # => 4
> 2 * 2   # => 4
> 3 / 2   # => 1 # Note the lack of decimals
> 5 % 3   # => 2
> 6 - 2   # => 4
> 5 ** 2  # => 25

The exponentiation operator ** is new, and raises a number to the nth power.

Floating Point Numbers

For floating point numbers, Ruby also resembles Javascript.

> 3.0 / 2     # => 1.5
> 0.15+0.30   # => 0.44999999999999996

Ruby even has NaN and Infinity, but only for floating point numbers. Integers generate exceptions in the same circumstances instead.

> 5 / 0
    ZeroDivisionError: divided by 0
> 0 / 0
    ZeroDivisionError: divided by 0

> 5.0 / 0   # => Infinity
> 0.0 / 0   # => NaN


Ruby's comparison operators should also look familiar, with one significant change:

> 7 == 7      # => true # Note: Only two equal signs
> 6 > 4       # => true
> 8 < 9       # => true
> 10 != 20    # => true
> 15 <= 13    # => false
> 8 >= 2      # => true
> 8 >= 2 && 15 <= 13  # => false
> 8 >= 2 || 15 <= 13  # => true


There are all kinds of neat things you can do with strings in Ruby. For example:

> "hello".capitalize    # => "Hello"
> "HELLO".downcase      # => "hello"
> "hello".reverse       # => "olleh"
> "hello" * 3           # => "hellohellohello"
> "hello".upcase.reverse  # => "OLLEH"

Notice the last example: You can absolutely chain methods in Ruby.

Simple Variables

Ruby's variables behave a lot like the ones in Javascript. Note that you don't need to remember the var busywork before you first use a variable. So in that essence Ruby doesn't care about declaring variables, they spring up into existence the first time they are seen in the code.

Example in IRB:

> x                 # => ERROR  
> x = 1             # Note: no var (unlike Javascript)
> x                 # => 1
> x = 'foo'
> x                 # => "foo"
> x = x + ' bar'    # => "foo bar"
> x                 # => "foo bar"


Arrays are ordered collections of objects. A variable, for instance, can hold only one item at a time. Arrays can hold multiple items. These items are called elements of the array. Arrays can hold objects of any data type and each element can be referred to by an index. Arrays are zero based, so the index of the first element is zero.

Example of an Array:

nums = [8, 9, 10, 11, 12, 13]

Working with Arrays

Like strings you can call methods on an array to interact with it.

Examples in IRB:

> nums.length   # => 6
> nums.first    # => 8
> nums.last     # => 13
> nums.reverse  # => [13, 12, 11, 10, 9, 8]

> nums[2]       # => 10
> nums[6]       # => nil
> nums[88]      # => nil
> nums[2] = 100 # => [13, 12, 100, 11, 10, 9, 8]
> nums[88] = 23 # => [13, ..., 23]
> nums.length   # => 89

> [1, 2, 3] << 99 # => [1, 2, 3, 99]

The append operator, <<, (a.k.a. "the shovel") basically sticks something at the end of the array. The difference here is that we dont have to specify an index position when using the append operator.

It's good to note that the num array is not permanently changed by calling the method reverse on it. It returns a new array with the elements reversed.


Now on to hashes. A hash is a collection of unique keys and their values, in other words, it's like a dictionary of key value pairs and can be easily created by using its implicit form:

burger_rating = { "Bacon Burger" => 10, "Guacamole Burger" => 9 }

Hashes allow an alternate syntax form where your keys are always symbols. Instead of

order_form = { :number_of_tacos => 10, :meat_type => "Carne Asada" }

You could write it as:

order_form = { number_of_tacos: 10, meat_type: "Carne Asada" }

Each named key is a symbol you can access in the hash:

order_form[:number_of_tacos]  # => 10

A Hash can also be created through its ::new method:

burger_rating =
burger_rating["Double Cheese Burger"] = 10

Hashes have a default value that is returned when accessing keys that do not exist in the hash. If no default is set nil is used. You can set the default value by sending it as an argument to ::new:

User-facing Functionality

So let's look at some more predefined methods that will be useful.

In Javascript we used code like console.log and alert when trouble shooting and prompt when we wanted user inputted information. Similar commands in Ruby are puts, print and gets.


The puts (short for "put string") and print commands are both used to display the results of evaluating Ruby code. The primary difference between them is that puts adds a newline after executing, and print does not.

Example in IRB:

print "Hello World"
Hello World # => nil

puts "Hello World"
Hello World
# => nil

In the example you can see differences and the newline the puts method adds.


The gets method gets a string from the keyboard. So, like in Javascript, where you have prompt, Ruby has gets. And just like Javascript and prompt, you are going to want to store input from gets in a variable so you can access it later.



The moment you hit return IRB is going to run the code and wait for user input to store in the variable.

Example in IRB:

a = gets
Hello World #irb waits for user input on this line and for you to hit return to store it.
# => "Hello World/n"

How come the new line /n at the end of Hello World? Its because gets takes the string that you typed along with the RETURN key pressed to end your input.

How do we get rid of it? Ruby has another method for just such an occasion. Its called chomp. The chomp method gives you back the string, but without the terminating newline /n.


a = gets.chomp
Hello World #irb waits for user input on this line and for you to hit return to store it.
# => "Hello World"

String Interpolation

It is essential to be able to replace placeholders within a string with values they represent. In the programming paradigm, this is called "string interpolation". In Ruby, string interpolation is extremely easy.

a = 1
b = 4
puts "The number #{a} is less than #{a + b}"
The number 1 is less than 5

This only works with "", not '' strings:

puts 'The number #{a} is less than #{a + b}'
The number #{a} is less than #{a + b}

Defining Methods

Simple Method

You can define your own methods, which as you know, are used to split your code into smaller bits of functionality and a way to use that functionality at a later time when needed.

Say I wanted to puts Hello World! numerous times, but dont want to write it out every time. Well, I can define a method.


def hi
  puts "Hello World!"

The code def hi, defines the method and gives it the name of hi. In between is the body, the code that I want to execute, and then the end tells Ruby we are done defining the method.

Now we can call the method repeatedly.

Example in IRB:

Hello World!
Hello World!
Hello World!

When defining methods with variables within them, those variables stay local to just that method.

def hi
  me = "This is so much fun"
  puts me

> hi
~> This is so much fun
> me
    NameError: undefined local variable or method `me' for main:Object
    from (irb):2
    from /Users/adam/.rvm/rubies/ruby-2.2.1/bin/irb:11:in `<main>'

Method with Parameters

Methods can also take parameters:

def add(a, b)
  a + b

Ruby simply returns the value of the last line of a method (no return needed or wanted in general).

To call the method:

> add(1, 2)   # => 3
> add 1, 3    # => 4

Parentheses are optional (but please use them to make your code easier to read).

Object Orientation

Ruby is an object-oriented language. Ruby is so object-oriented that a common Ruby mantra is: "Everything is an object."

But what does that mean?

It's a bit tricky to explain what an "object" is; but, loosely speaking, it's a thing that you send a message to. All the action in Ruby happens because you send a message to an object.

In order for an object to respond meaningfully to a message, it must somehow possess internal knowledge of that message a pre-existing, primed response, saying what should happen when this particular message arrives.

This primed response is called a method. In other words, a method is simply a set of instructions saying what an object should do in response to a particular message.

To send a particular message to an object is to call that method of the object.

Calling Methods on Objects. The DOT!

In Ruby, you call a method to an object using the dot-notation: first the name of the object, then a dot, then the method. For example, if we had an object called Dog, we could call the method for it to bark like this:


That's a legal Ruby program in theory, but in fact it wont do anything useful all by itself. Right now, if you were to run that as a Ruby program, Ruby would give you an error message. That's because we dont have an object called Dog. And even if we did, it wouldnt necessarily know how to bark because there is no method called bark.

Let's try it with a real Ruby object like "Hello". You will notice that "hello" is a string. A string is an object that Ruby knows. So that means the string has a pre-existing, primed responses to certain messages.



The string "hello" knows when the upcase method is called on it, it needs to change all letters to an upper case.

Given Classes

We've established everything in Ruby is an object; and just like real world objects you can make them do something; "." means calling a method on (doing something to) an object.


Every object in Ruby belongs to a class: (another way of saying: each object is an instance of class). To find out what class an object is a part of you can call .class on any object and it will tell you. Once you know it is easy to Google the class of Ruby and see the methods/capabilities of the class.


Do this for yourself to see the Ruby documentation:
Google: Ruby String class
Google: Ruby Fixnum class

Be sure to select the documentation for the version of Ruby you have installed (to find out use: ruby --version).

Loops and Blocks

Ruby has loops somewhat like the ones in Javascript (for, while and such), but experienced Ruby developers mostly use some different and easier-to-use sorts of loops. Let's examine the major ones.

.times Loop

We saw this already in an earlier lesson. If you want to repeat some code a certain number of times, you do this (note that p x in Ruby means "print out the value of x").

> x = 5
  # => 5
> x.times do
>     puts 'hello'
?>   end
  # => 5

Just as with Javascript, every function or method we call returns some sort of value. Ruby's built-in functions generally try hard to find something useful to return, and often they do this by giving you the last value they worked with. So in this case, a times loop returns how many times it ran.

.each Loop

Ruby's each also lets you do something with every element of an array.

> a = [1, 2, 3]
> a.each do |element|
      puts element
  # => [1, 2, 3]
  > x
  NameError: undefined local variable or method `x` for main:Object
> a   # => [1, 2, 3]

Note the original array is untouched.

.each loop with a Hash and string interpolation

.each calls block once for each key in the hash, passing the key-value pair as parameters.

If no block is given, an enumerator is returned instead.

burger_rating = { "Bacon Burger" => 10, "Quacamole Burger" => 9 }
burger_rating.each {|key, value| puts "The #{key} has a rating of #{value}" }


The Bacon Burger has a rating of 10
The Quacamole Burger has a ratting of 9


Ruby's map also lets you do something with every element of an array; it
returns a new array filled with whatever gets returned by the block each time it runs:

> a = [1, 2, 3]
> { |n| n * n } # => [1, 4, 9]
> a                   # => [1, 2, 3]

Note the original array is untouched


Ruby has two simple ways of creating anonymous functions similar to Javascript; they are called blocks:

nums.each() { |element| puts element }      
nums.each() do |element|
   puts element
   # Place more lines here

These blocks are equivalent. Use the {...} for one line blocks and the do ... end for multi-line blocks.

Blocks can have multiple parameters:

nums.each_with_index() { |element, index| puts index }

nums.each_with_index() do |element, index|
   puts index.to_s +   + element.to_s

if, else

Ruby has quite a few more ways of branching than Javascript does, but they're simpler to use on the whole.

There is a simple if-else construct similar to Javascript.

x = 1
if x == 3
  puts "Huh?"
  puts "Just confused now."


When you need more than an either/or. elsif indicates an alternative to the preceding if and any other preceding elsif statements. So, you start off with the if, have any number of elsif alternatives, and end with an else to capture all the leftover possibilities. In Javascript it was spelled out as: else if.

x = 1
if x == 2
  puts "Double huh?"
elsif x == 1
  puts "That's right."
  puts "Just confused now."

We write elsif rather than Javascript's else if and you don't need the parentheses, but its otherwise pretty similar.


There's also an unless, which is just like if !(...). The unless keyword is just if in reverse. Its a conditional statement that executes only if the condition is false, instead of true.

x = 1
unless x > 1
  puts "Okay"
  puts "Huh?"

# => Okay

The statement above with an if statement would have to look like below to get the same output.

x = 1
if !(x > 1)
  puts "Okay"
  puts "Huh?"

~> Okay

I think if I was going to have an else there, I would switch the above example to use an if
You can write if or unless at the end of a line, in which case it controls whether that line is executed.

x = 1
puts "Huh?" unless x == 1
# => nil

puts "Okay" if x > 0
# => nil

Derek Banas' Ruby Tutorial Ruby in One Video

Ruby Basics Challenge

Arithmetic Challenge

Remember that floats are numbers with a decimal point whereas integers have no fractional part so in Ruby, 1 and 1.0 are different types of things with slightly different behaviors.

Just as you did with Javascript, try these, both with integers and floats:

  • Add, subtract, multiply and divide some numbers any combination of numbers
  • Find the remainder of dividing two numbers using the modulo operator (%)
  • Divide a number by 0
  • Divide 0 by 0

Variables Challenge

Here are a few exercises for you to practice using variables:

  • Set a variable called my_favorite_number equal to your favorite number.
  • Calculate what your favorite number divided by 2 is.
  • Set another variable called someones_favorite equal to 13
  • Change the value of someones_favorite to 7
  • Subtract your favorite number from someones
  • Change the value of my favorite number to be 26 times its current value

Strings Challenge

For this exercise, try out some of the Ruby string methods for yourself.

  • .upcase
  • .reverse
  • .include?
  • capitalize
  • create a variable and put it into a string using string interpolation

Arrays Challenge

Read the introductory information about the pretty comprehensive set of Array features Ruby has.

  • Create an array with ten of your favorite movies
  • From that array, extract your top 3 movies in a new array
  • Find an expression that tells you how many elements are in the array
  • Reverse an array, try out slices, how to rotate them, and how to get a random element from the array
Ruby Decision Structures Challenge


  • Write a loop that prints from 1 to 20. Try it with all the loops covered in this lesson. Do it again counting down from 20 to 1.
  • Write a program which takes a number and prints "Valid" if the number is between 1 and 10 (inclusive) and "Invalid" otherwise.
  • Write a program that prints the numbers from 1 to 100. But for multiples of three print Fizz instead of the number and for the multiples of five print Buzz. For numbers which are multiples of both three and five print FizzBuzz
  • Create a method called sum_these_numbers which takes two integers as an argument and prints their sum to the screen.
  • Create a method called is_even, which takes a single integer, and which then returns true if the number is even, and false otherwise.
  • Create an array of words. Iterate through the array using .each and a block, then print each of those words in all capitals.
  • Write a method which calls another method, then uses its return value.
  • Write a function called valid_date that prompts the user for a date with a month, date, and year (all numerically expressed) and returns 'true' if this date exists and 'false' if it does not (for example: 7 28 2014 exists, but 22 34 1999 does not). Make sure to account for leap years. This program is easiest if you prompt for the month, date, and year separately.
  • Using if, elsif, and else blocks, write a function called rps_game which allows two users to input their moves in "Rock, Paper, Scissors" and which determines the winner (or if a tie occurred).
Password Checker Challenge


You are writing the user registration page for a secure web site.
On the registration page, the user has to enter a user ID and a password, which has to adhere to the to following criteria:

  • User ID and password cannot be the same
  • User ID and password have to be at least six characters long
  • Password has to contain at least one of: !#$
  • User ID cannot contain the following characters: !#$ and space
  • Password cannot contain "password" in a capitalization

Proceed as follows:

Challenge: Write a function called same that takes a user ID and a password, and returns true if they are, and false otherwise.

same("joe", "joe") -> true
same("joe", "joe1") -> false

Challenge: Write a function called long_enough that checks whether a String is at least six characters long, and returns true if it is, and false otherwise.

long_enough("12345") -> false
long_enough("123456") -> true

Challenge Write a function called does_not_contain_special which checks to see if !, #, $ is not contained in a given String.

does_not_contain_special("Hello Friend") -> true
does_not_contain_special("A#C") -> false
does_not_contain_special("A!C") -> false
does_not_contain_special("A$C") -> false

Challenge Write a method called contains_special which checks to see if !, #, $ is contained in a given String.

contains_special("Hello Friend") -> false
contains_special("A#C") -> true
contains_special("A!C") -> true
contains_special("A$C") -> true

Challenge Write a method that inputs user ID and password from the user, and then tells the user if the they are acceptable.
Write a main method called validate_password that:

  • First lets a user input both user ID and password,
  • Then use the methods above to evaluate if the user ID and password combination is acceptable or not
  • Tells user what the result is.

Stretch Goal

  • Password has to contain at least one digit Task: Write a function using basic functions on String to see if a given String contains contains one of "0","1", "2", "9". Tests:
has_digit("abc") -> false
has_digit("a1c") -> true

Super Stretch Goal

  • Password has to contain a lower and an uppercase letter. Tests:
has_upper_and_lowercase("abc") -> false
has_upper_and_lowercase("aBc") -> true
has_upper_and_lowercase("123") -> false

Today's Tentative Schedule

9:15am - Stand Up

9:30am - Introduction to Ruby: Derek Banas' Ruby Video including Basic Data Types, User-Facing Functionality, Methods, Objects, Loops, Blocks

12:00 noon - Lunch

1:00pm - Ruby Basics Challenge

4.30pm - Review

5:00pm - Class Ends