Intro to Ruby - Twin Cities Code Camp 7

intro to ruby
brian hogan
New Auburn Personal Computer Services LLC

you just don’t know it
yet.

I was a designer. I hated
programming.

my clients wanted
interactive websites...

and I started to hate
my life.

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

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

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

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>

!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

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

got a big site that’s hard
to maintain?

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)

Ruby follows the
Principle of Least
Surprise.

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

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"}

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

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

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

Every professional Ruby
developer writes tests
ﬁrst for production
code.

Ten Simple Rules
For Programming in
My Favorite Language.

1. Everything is an
object

25.class Fixnum

"brian".class String

[1,2,3].class Array

2. Everything evaluates
to true except nil or
false

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!

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

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

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

WRONG!
person = new Person

RIGHT!
person = Person.new

7. You need to use and
understand blocks.

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

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.

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!"

person.respond_to?(:name) true

person.respond_to?(:age) false

person.send(:name) “Brian”

10. Write code that
writes code.

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
!!!
#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; }

Hello Sinatra!

require 'rubygems'
require 'sinatra'

get "/" do
"Hello Sinatra!"
end

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!"

Testing the Wiki with
Webrat and Cucumber

Ruby will make you
productive.

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/

Questions?
Twitter: bphogan
bphogan at gmail

Intro to Ruby - Twin Cities Code Camp 7

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