A Quick Intro to Ruby by Nicolas McCurdy 

What is Ruby? Ruby is a programming language that is… ● dynamically typed ● object oriented ● flexible ● inspired by many features of other languages 

Hello World puts “Hello, world!” Note that, similarly to Python, code doesn’t have to be in a class, method, or module. This makes Ruby very useful for scripting. Running from a file: ruby hello.rb 

Methods def double(number) number * 2 end # Note that parentheses for method calls are optional double 5 # 10 # This also works double(5) 

Methods with Optional Arguments def greet(name = “Ruby”) puts “Hello, I am #{name}.” end greet # Hello, I am Ruby. greet “Nick” # Hello, I am Nick. 

Simple Types Strings ● “Hello” or ‘Hello’ ● Mutable. Numerics ● 4 or 4.0 ● Note that Fixnums and Floats are two separate subclasses of Numerics. Booleans ● true or false Symbols ● :green ● Immutable. ● Useful for representing an arbitrary value (use this where you want an enum or a String that represents an arbitrary value but isn’t displayed). 

More Types Arrays ● [“One”, 2, :3] ● Arrays are dynamically typed, so they can contain values of different types. ● Arrays are more like what other languages call “lists”, since they can be modified. Ranges ● 0..10 ● Can be used to into into an array like this: array[0..10] Hashes ● person = { “Name” => “Bob”, “Age” => 15 } ● Like a dictionary or hash map in other languages. ● person = { name: “Bob”, age: 15 } ● name: “Bob” is the same as :name => “Bob”, but easier to read and write. ● Looking up a value: person[:name] 

Classes # Create the Person class class Person def initialize(name) @name = name end attr_reader :name def greet(other) puts “Hello #{other.name}, I am #{@name}.” end end # Create two people that will greet each other matz = Person.new(“Yukihiro Matsumoto”) david = Person.new(“David Heinemeier Hansson”) matz.greet(david) # output: Hello Yukihiro Matsumoto, I am David Heinemeier Hansson. 

Modules # Add to Ruby’s existing Math module module Math def self.double(number) number * 2 end end # Call the method directly off the module Math.double(5) # Output: 10 

Additional Resources ● tryruby.org ● ruby-lang.org/en/documentation/ ● irb