Welcome!

What we will cover today

• What is programming?
• Why Ruby?
• Variables, Arithmetic & Objects
• Methods and Error Messages
• REPLs and Installing Ruby

About Me

• Ryan Dlugosz (duh-LOO-gus... it's Polish)
• Independent Consultant, Ruby (mostly)
• ryan@dlugosz.net
• GDI Slack: @ryandlugosz / #intro-to-ruby

About the TAs

TBD

About YOU!

Our facilities today…

• Restrooms - Down the first hall on the left.
• Refreshments - Help yourself! PS – Thanks Cardinal!
• Please step out to take a call.

Why Ruby?

Ruby is a Powerful language that reads like English!

Designed for Programmer Happiness!

Welcoming, friendly community!

> Ruby.easy_to_learn? and Ruby.fun_to_use?
=> true

What do you think this Ruby code does?

ruby> 1 + 1

   => 2

Okay, that was pretty easy… Try this one!

What does this code do?

ruby> puts "Hello World!"

Hello World!

Let's say it three times!

ruby> 3.times do
        puts "Hello World!"
      end

Hello World!
Hello World!
Hello World!

Cool, huh?

Let's start coding for real!

Intrigued?

Let's talk in more detail about some of the things we learned.

Using a REPL

• Try Ruby is a REPL
• Read, Evaluate, Print, Loop

repl.it

repl.it is an online REPL that supports several different languages. It's a great place to try things, and makes it easy for us to share links to our code in class.

Visit the repl.it site and select "Ruby" from the menu.

Working with IRB

(optional)

• IRB (Interactive RuBy) is a command line interface to ruby that is installed when we install Ruby. It works like a calculator and is a great way to get started quickly.
• Open: type `irb`
• Quit: Type `quit` and then press `enter`
• Feel free to explore. You will not accidentally break things!

Arithmetic

Try out some calculator functions

              
3 + 4
2 * 4
6 - 2
4 / 2
4 /* 2
=> SyntaxError: (irb):10:syntax error, unexpected *
              
            

Arithmetic

Other Ruby Math Operators

# Modulo operator (returns the remainder)
11 % 5
=> 1

# Exponent operator (2 raised to the power of 3)
2 ** 3
=> 8
              

Variables

• Variables are references to information.
• We reference variables by name.
• They are called variables because theinformation they reference may change.

# Everything after the pound sign will not be evaluated.
# These are called comments and I will use them to annotate code
age = 50
days_in_year = 365
days_alive = age * days_in_year
=> 18250

Variables, Constants, Symbols

• Ruby has variables, constants and literals.
• A variable starts with a lower case letter and multiple words are separated with an underscore character (_), like_this.
• Constants do not change and are typically written in all caps.
• A symbol is a shorthand for a constant string.
• Literals are literal values, for example the number 3 or the string 'hi'.

# variables
age = 37
instructor_name = "Ryan Dlugosz"

# constants
BEST_FOOD = "Sushi"
PI = 3.14159

# symbols
:pizza
:ice_cream

# literals
3
'hi'
          

What can I do with a Variable?

• Create - Initialize - Define
• Access - Read
• Assign - Replace

# create and assign in one line
age = 0

# access the value in age
age

# replace value in age
age = 40

# use it in a statement
age + 10        # => 50
          

Variable naming

• Make it meaningful
• Make it easy to read
• Make it concise
• Should be unique
• Should be understood by someone who has no idea what your program does

# good
occupation = "software developer"


# bad
occupation_i_always_dreamed_of_having_in_cincy = "software developer"
o = "software developer"
1st_occupation = "software developer"

          

Local Variable Values

• No default value
• No type declaration
• Do not live forever

# error
name


  # defined, initialize, create
  name = "KC"
  defined?(name)      # => true

          

Data Types

Numbers   |   Strings   |   Symbols   |   BooleansRegular Expressions   |   Arrays   |   Ranges   |   Hashes

• Data always has a "type"
• You will hear the words Class/Type/Object used interchangeably
• Let's explore a few built in Objects

          irb> 1.class
          => Fixnum

          irb> "Hello".class
          => String

          irb> 1.0022.class
          => Float

          irb> [1,2,3].class
          => Array
          

Numbers

Numeric data comes in two types: Integers and Floats

            irb> 1_000_000_000_000_000_000.class
              => Fixnum
            irb> 1_000_000_000_000_000_000_000.class
              => Bignum
          

            irb> 1.001.class
              => Float
          

Number Practice

          7/8
          7.0/8.0
          3.14.to_s
          3.14.to_i
          1 + "2"
          1 + "2".to_i
          (1 + 2) * 3
          1 + (2 * 3)
          

How many seconds are in an hour?

How many minutes are in a week?

How many years old are you if you've been alive 1 million seconds?

Strings

Strings are characters inside double or single quotes.

          a = 'Hello '
          b = "World"
          c = a + b
          c.reverse
          => "dlroW olleH"
          

          a = "Spam "

          # Here multiplying a by 4 concatenates (links) four strings together
          b = a * 4
          =>"Spam Spam Spam Spam "
          

String Practice

          "Heather".upcase
          "Heather".downcase
          "heather".capitalize
          "Hello".reverse
          "Heather".length
          "Heather Moore".swapcase
          "".empty?
          

What is the reverse of your name?

How many characters long is your name?

Can you repeat the word hello 100 times?

What is the 5th character of my name?

Methods

• Methods define the behavior for an Object.
• The "." is an operator that connects the Object of the method to the method.
• String Objects can reverse, for example.
• Let's call some methods

          irb> puts "hello"
          hello
          => nil

          irb> "2".to_i
          => 2

          irb> 2.to_s
          => "2"

          irb> "2" / 5
          NoMethodError: undefined method `/' for "2":String
            

User Input

• To obtain user input, use gets
• To print out information, use puts
• Let's create our first program together

                      puts 'Hello there, and what\'s your name?'
                      name = gets
                      puts 'Your name is ' + name.chomp! + '? What a lovely name!'
                      puts 'Pleased to meet you, ' + name + '. :)'
                      

                        ruby name.rb
                      

Installing Ruby

(supplemental)

The following slides are included for reference, but are not required steps for completing this Intro to Ruby class. If you have any trouble, please ask me for help in the GDI Slack channel.

Using a Mac?

If you happen to be using a Mac, Ruby is already installed on your computer!

Using a Windows PC?

Download and run the Rails Installer for Windows (Ruby 2.2 version).

RailsBridge Installfest

The RailsBridge organization maintains a great resource for installing Ruby on your computer. Check it out!

These instructions could be helpful if you run into trouble.

http://docs.railsbridge.org/installfest/

Just work through the instructions for your operating system. For our class, you'll only need to advance through the first steps, but you're welcome to advance further if you're curious or plan to write a Rails applications.

Intro to Terminal

Working in the terminal can be really intimidating at first!

With practice, navigation and file manipulation is significantly faster in the terminal than in the GUI.

Professional software developers use the terminal all the time, and this class will require some use of it.

Intro to Terminal

Mac & Linux users: Open Terminal

Windows users: Open Git-Bash

We will not be using Windows "cmd" program, as it uses a different syntax than *NIX systems.

Intro to Terminal Prompt

The line that appears in the terminal when you open it is called the prompt. It usually contains information about the user and current directory. It can be customized.

Terminal instructions often start a line with a $. This represents the last character in the prompt, you don't have to type it.

Terminal Cheatsheet

Terminal Activities

  # navigate to your desktop
  cd ~/Desktop    #Linux, Mac
  cd desktop      #Windows

  # make a directory called ruby_adventures
  mkdir ruby_adventures

  # navigate into new directory
  cd ruby_adventures

  # create a file
  touch class0.rb

  # list the contents of the directory
  ls
            

Terminal Activities

    man ls
            

Output:

End of Day 1!!!

Homework!

• Join GDI Slack & #intro-to-ruby
• Complete the Hour of Code
• Explore more of the Try Ruby challenges
• Bonus: Chapters 0–6 of Learn to Program
  • While you can follow the book's instructions and install Ruby on your computer, you may find it easier to use the online tool repl.it

Next Week

• Review homework
• Flow control (if/then/else and friends)
• Arrays and Hashes
• Looping and Enumeration

Upcoming Events