Intro to Ruby

intro to ruby
brian hogan
New Auburn Personal Computer Services LLC

twitter: bphogan
email: brianhogan at napcs.com

programming is fun.

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you just don’t know it
yet.

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I was a designer. I hated
programming.

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my clients wanted
interactive websites...

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and I started to hate
my life.

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I learned Ruby in 2005
and fell in love...

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So what can kinds of
things can you do with
Ruby?

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Shoes.app do
para "Item name"
@name = edit_line

button "Add to list" do
@names.append do
para @name.text
end
@name.text = ""
end

button("Clear the list") {@names.clear}

@names = stack :width=>"100%", :height=>"90%"

end

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require 'sinatra'
require 'pathname'

get "/" do
dir = "./files/"
@links = Dir[dir+"*"].map { |file|
file_link(file)
}.join
erb :index
end

helpers do

def file_link(file)
filename = Pathname.new(file).basename
"<li><a href='#{file}' target='_self'>#{filename}</a></li>"
end

end

use_in_file_templates!

__END__

@@ index
<html>
<head>
<meta name="viewport" content="width=320; initial-scale=1.0; maximum-scale=1.0; user-scalable=0;"/>
<style type="text/css" media="screen">@import "/stylesheets/iui.css";</style>
<script type="application/x-javascript" src="/javascripts/iui.js"></script>
</head>

<body>
<div class="toolbar">
<h1 id="pageTitle"></h1>
</div>
<ul id="home" title="Your files, sir." selected="true">
<%= @links %>
</ul>
</body>

</html>

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!the_border = 1px
!base_color = #111
#header {
#header color: #333333;
color = !base_color * 3 border-left: 1px;
border-left= !the_border border-right: 2px;
border-right = !the_border * 2 color: red; }
color: red #header a {
font-weight: bold;
a text-decoration: none; }
font-weight: bold
text-decoration: none

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got a great idea and
want to get it out there
quickly?

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got a big site that’s hard
to maintain?

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So, what is Ruby?
• Highly dynamic
• Very high level
• 100% object oriented
• 100% open-source
• Really easy to learn

History

Smalltalk C++ Ruby Java VB 6 C#
(1983) (1989) (1993) (1995) (1996) (2000)

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Ruby follows the
Principle of Least
Surprise.

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consistent API
"Brian".length
["red", "green", "blue"].length
[:first_name => "Brian", :last_name => "Hogan"].length
User.find_all_by_last_name("Hogan").length

and a simple syntax
age = 42
first_name = "Homer"
start_date = Date.new 1980, 06, 05
annual_salary = 100000.00

Basic Ruby

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Standard operators

5 + 5
10 * 10
"Hello" + "World"
25 / 5

Arrays

colors = ["Red", "Green", "Blue"]

Hashes (Dictionaries)

attributes = {:age => 25,
:first_name => "Homer",
:last_name => "Simpson"}

:foo

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Simple control logic
if on_probation(start_date)
puts "Yes"
else
puts "no"
end

Unless
if !current_user.admin?
redirect_to "/login"
end

unless current_user.admin?
redirect_to "/login"
end

Conditionals as statement sufﬁxes

redirect_to "/login" unless current_user.admin?

Methods (functions) are simple too.

# if start date + 6 months is > today
def on_probation?(start_date)
(start_date >> 6) > Date.today
end

Classes are easy too.
class Person
@started_on = Date.today
@name = ""

def started_on=(date)
@started_on = date
end

def started_on
@started_on
end

end

Class instance variables are private
class Person
Expose them through
@name = ""
accessor methods that
@started_on = date resemble C# and VB
end
Property members.
def started_on
@started_on
end person = Person.new
person.age = 32
def name=(name) person.name = "Brian"
@name = name
end
person.age
=> 32
def name person.name
@name
=> "Brian"
end
end

Let Ruby write code for you!
class Person
@name = ""

class Person
@started_on = date
end attr_accessor :name
attr_accessor :started_on
def started_on
@started_on end
end

def name=(name)
@name = name
end

def name
@name
end
end

Ruby is a loaded gun.

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So, write good tests.

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TATFT

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def test_user_hired_today_should_be_on_probation
person = Person.new
person.hired_on = Date.today
assert person.on_probation?
end

test_user_hired_last_year_should_not_be_on_probation
person = Person.new
person.hired_on = 1.year.ago
assert !person.on_probation?
end

Implement the method
class Person
attr_accessor :name, :start_date

def on_probation?
(start_date >> 6) > Date.today
end
end

And the tests pass.

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Testing ﬁrst helps you
think about your design
AND your features.

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Every professional Ruby
developer writes tests
ﬁrst for production
code.
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Ten Simple Rules
For Programming in
My Favorite Language.

1. Everything is an
object

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25.class Fixnum

"brian".class String

[1,2,3].class Array

2. Everything evaluates
to true except nil or
false

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x = 0
0
puts x if x

x = -1
-1
puts x if x

x = false
nil
puts x if x

x = nil
nil
puts x if x

3. Variables are
dynamically typed but
DATA is strongly typed!

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age = 32
name = "Brian" TypeError: can't convert Fixnum into String
name + age

age = 32
name = "Brian" “Brian32”
name + age.to_s

4. Every method
returns the last
evaluation implicitly

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def limit_reached?
self.projects.length > 0
end

def welcome_message
if current_user.anonymous?
"You need to log in."
else
"Welcome!"
end
end

5. Every expression
evaluates to an object

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result = if current_user.anonymous?
"You need to log in."
else
"Welcome!"
end

It is very easy to accidentally return false!
def before_save
if self.status == "closed"
self.closed_on = Date.today
end
end

6. Classes are objects

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WRONG!
person = new Person

RIGHT!
person = Person.new

7. You need to use and
understand blocks.

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Blocks can iterate

roles.each do |role|
puts "<li>" + role.name + "<li>"
end

They can also encapsulate code.

ActiveRecord::Schema.define do
create_table :pages do |t|
t.string :name
t.text :body
t.timestamps
end
end

Every method can take a block!

5.times do
puts "Hello!"
end

8. Favor modules over
inheritance

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module SharedValidations
def self.included(base)
base.validates_presence_of :name
base.validates_uniqueness_of :name
end
end

class Project class Task
include SharedValidations include SharedValidations
end end

Do not use type,
use behaviors.

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module Doctor module Ninja
def treat_patient def attack
puts "All better!" puts "You’re dead!"
end end
end end

module Musician
def play_guitar
puts "meedily-meedily-meedily-meeeeeeeeee!"
end
end

person = Person.new
person.extend Ninja "You're dead!"
person.attack

person.extend Doctor
"All better!"
person.treat_patient

person.extend Musician "meedily-meedily-
person.play_guitar meedily-meeeeeeeeee!"

9. Embrace Reﬂection

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person.respond_to?(:name) true

person.respond_to?(:age) false

person.send(:name) “Brian”

10. Write code that
writes code.

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class User
ROLES = ["admin", "superadmin", "user", "moderator"]
ROLES.each do |role|
class_eval <<-EOF
def #{role}?
self.roles.include?("#{role}")
end
EOF
end
end

user = User.new
user.admin?
user.moderator?

haml and sass

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HAML
!!!
#wrapper.container_12
#header.grid_12
%h1 The awesome site
%ul#navbar.grid_12
%li
%a{:href => "index.html"} Home
%li
%a{:href => "products"} Products
%li
%a{:href => "services"} Services
#middle.grid_12
%h2 Welcome

#footer.grid_12
%p Copyright 2009 SomeCompany

HTML
<div class='container_12' id='wrapper'>
<div class='grid_12' id='header'>
<h1>The awesome site</h1>
</div>
<ul class='grid_12' id='navbar'>
<li>
<a href='index.html'>Home</a>
</li>
<li>
<a href='products'>Products</a>
</li>
<li>
<a href='services'>Services</a>
</li>
</ul>
<div class='grid_12' id='middle'>
<h2>Welcome</h2>
</div>
<div class='grid_12' id='footer'>
<p>Copyright 2009 SomeCompany</p>
</div>
</div>

SASS

!the_border = 1px
!base_color = #111

#header
color = !base_color * 3
border-left= !the_border
border-right = !the_border * 2
color: red

a
font-weight: bold
text-decoration: none

CSS

#header {
color: #333333;
border-left: 1px;
border-right: 2px;
color: red; }

#header a {
font-weight: bold;
text-decoration: none; }

StaticMatic demo

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sinatra

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Hello Sinatra!

require 'rubygems'
require 'sinatra'

get "/" do
"Hello Sinatra!"
end

Sinatra demo

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cucumber

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Feature: creating a new page in the wiki
As an average anonymous user
I want to create a page about Ruby
So that I can tell everyone how awesome it is.

Scenario: Creating a new page and editing its content
Given I go to "/ruby"
Then I should see "Edit this page"
When I click "Edit this page"
And I fill in "body" with "Ruby is the best programming language in the whole world!"
And I press "Save"
Then I should see "Ruby is the best programming language in the whole world!"

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Testing the Wiki with
Webrat and Cucumber

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Ruby will make you
productive.

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And happy.

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Resources:
Try Ruby in your browser! http://tryruby.sophrinix.com/
Try SASS online: http://sass-lang.com/try.html
Try HAML online: http://haml-lang.com/try.html
http://staticmatic.rubyforge.org/
Sinatra: http://www.sinatrarb.com/
Sinatra Wiki source: http://github.com/napcs/sinatriki
Cucumber: http://cukes.info/
WATIR: http://watir.com/

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Questions?
Twitter: bphogan
brianhogan at napcs.com

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