Ruby Programming Introduction

A partial introduction to the
^
The Ruby Programming Language
by Anthony W. Brown

Tuesday, March 26, 13

Introduction

This presentation is an adaptation from “The
Ruby Programming Language” by Matz and the
University of Washington’s Ruby and Rails PCE
course.

This deck was originally intended to cover all object-oriented principles, popular
tools and the Rails framework. If anyone likes this deck, I will create rest for
you...


Useful Links

• http://www.ruby-doc.org/
• http://apidock.com/ruby
• http://apidock.com/rspec
• http://zenspider.com/Languages/Ruby/
quickref.html


Origins
“Ruby is simple in appearance, but is very complex
inside, just like our human body”
-Matz


Ruby is...

• Object Oriented
• Dynamic
• Reﬂective
• Interpreted


Ruby in a Slide

• TDD
• IRB
• Gems
• Bundler
• Rspec


Tools

• git, github
• RVM
• Ruby Gems
• RSpec
• Rake
• Guard


Install Check

awb - bash - 80x24
Last login: Sun Feb 10 11:28:48
macpro:~ awb$ git --version # Check git version
macpro:~ awb$ ruby -v # Check Ruby version, 1.9.3?
macpro:~ awb$ irb # Interactive Ruby Environment
macpro:~ awb$ gem install rspec
# Install the RSpec test tools


git

awb - bash - 80x24
macpro:~ awb$ git config # set or view configuration
macpro:~ awb$ git clone # copy repository
macpro:~ awb$ git init # make current dir a repo
macpro:~ awb$ git status # get current state or repo
macpro:~ awb$ git add # add items to index
macpro:~ awb$ git rm # remove items from index
macpro:~ awb$ git commit # commit index to repo
macpro:~ awb$ git push
# move commits to remoter server
macpro:~ awb$ git log
# list of commits in this repo


RSpec
http://rubydoc.info/gems/rspec-expectations/2.4.0/RSpec/Matchers

describe #describes “what” in a test
context #describes “when” in a test
it #performs an operation,“does”
should #Class attribute
eq #matcher
be_a #matcher
kind_of #matcher

awb - bash - 80x24
macpro:~ awb$ rspec -c -f d ‘filename’


Rake
Rake is Ruby’s version of make: a domain speciﬁc language to deﬁne tasks.
Easy to manage dependencies and tasks.

task :clean_update do =begin
system(clean_up_script.sh) Ruby version of make; A DSL to
MyClass.update_everything(‘./ define tasks
path’) Easy to manage dependencies and
end tasks
=end

awb - bash - 80x24
macpro:~ awb$ rake clean_update


Objects
Everything in Ruby is an object.

“hello” #string

4 #integer

[] #empty array

my_array

:symbol
#comment

=begin
multi-line comment
=end


Operators

- #Unary operators
!
*
~

+ - #Binary operators
* / **
<<
&& ||

my_variable? #Ternary operators
‘True’:


Assignment
Hold values, or references to objects.

# lvalue are assignment,rvalue
# are reference

a = b #lvalue = rvalue

a += 1 #abbreviated assignment same
#as a = a + 1

a, b = 1, 2 # a = 1, b = 2

a, b, c = [1,2] # a = 1, b = 2, c = nil


Expressions

‘hello’ =begin

File Expressions evaluate to and
return a value.
true
Compound expressions leverage
false an operator (+/-/*/%)
nil =end
self


Variables
Variables hold values, or references to objects
#initialize to prevent NameError
a = “Woof!”

b = a #b = “Woof!”

b.object_id #b = “Woof!”

c = a.dup #c = “Woof!”

b[0] = “P” #a and b = “Poof!” c still
#“Woof!”

#Local: my_var
#Global: $password
#Class: @@counter
#Instance: @name
#Constant: MY_CONST


Strings
Text is represented by strings, which are of class String.

’35’ #single-quoted string literal

“35” #double-quoted string literal

my_age = “35” #Assigned string variable

“ My age is #{my_age}” #Interpolation


Numbers
Ruby has 5 built-in classes for numbers in the standard library.

123456789 #Literal Objects

3.141519 #Class Hierarchy:

1,000,000,000,000 #Numeric

#Integer

#Fixnum

#Bignum


Arrays
Arrays are lists of values that can be accessed by their position.

my_array = [“1”, “2”, “3” =begin

1, 2, 3 Arrays are not typed, ordered,
mutable, literal, and
a, << “1”, “2”, “3” Enumerable.They contain many
operators and methods like:
my_array = []
+ << *
[]
.push .pop
Array.new
.sort.

.uniq!

=end


Hashes
Hashes are key/value pairs.

my_hash = {:a =>“1”, :b =>“2”} =begin

my_hash = {} Hashes like arrays are not
typed. They are ordered,and
{a: 1, b: “2”} Enumerable.They contain many
operators and methods like:
my_hash = [:a] = 1
=end
my_hash = [:b] = 2

Hash.new


Iterators
Like a loop, iterators perform operations on data sets.

3.times {puts “thank you!”} #

my_data.each { |x| print x} #

[1,2,3].map { |x| x*5} #


Methods
Methods pass messages to objects. They have 5 parts; the object, message,
parameter, block and body.

my_method #Various ways to call a method

my_method parameter

my_method (parameter)

my_method (parameter1, 2)

object.my_method

my_method par1, par2, do| #Syntax structure
block| tweet! “#{par1} just #object.method(parameter) {block}
did #{par2}”

end


Method Object
Objects receive messages. Every object has methods and self

def my_method; end #dangerous methods end in ‘!’

object.respond_to? :my_method # => true


Method Message
The Message is required. Style is to use snake_case naming conventions.

#predicate methods end in ‘?’

[].empty? # => true

my_method.uniq #dangerous methods end in ‘!’

my_method.uniq! doesn’t modify the method

does modify the method


Method Message
The Message is required. Style is to use snake_case naming conventions.
#predicate methods end in ‘?’
[].empty? # => true

#dangerous methods end in ‘!’
my_method.uniq #doesn’t modify the method
my_method.uniq! #does modify the method

def name = str #attribute setter method name end =
@name = str
end

class MyObject #index lookup (-ish) methods use []
def [] num
@collection[num]
end
end


Method Parameters

#0 or more, comma separated,
#defaults can be defined.
def say str1, str2, str3
“#{str1} --- #{str2}”
end

say ‘hi’, ‘bye’ # => ‘hi --- bye’


Blocks
Nameless function (arbitrary code) passed to a method with {code} or ‘do
code end’. Any method can receive a block.

def my_method par =begin
{|block_par| use block par}
end Blocks to not have to be named
as a parameter and are ignored
if not explicitly used by a
def my_dog method. The block passed
print “I’m a dog...” describes what to do with each
yield thing.
end
=end

run {print “Bark, bark!”} # => I’m a dog. Bark, bark!

#


Blocks
Example

module Enumerable # Calling Enumerable

def map # Create a method
result = [] # Assign a variable
self.each do |object| # Create a block
result << yield object
end
result
end

end

[1, 2, 3].map { |n| n * 2 } # => [2,4,6]


More to come. If you have any questions, please contact me on various social
media networks with the alias @awbrown.


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