Introduction to Ruby on Rails from my Ruby on Rails and PostgreSQL - Intro to Advanced class in August 2014.

1. Intro to Rails

2. What do we look for in a framework?
• Please don’t suck
– Rails does not suck
• Does it follow Model-View-Controller?
– Yes
– Since Rails 1 it’s been the standard bearer for how to do MVC on the web, copied in almost every language
• Does it help me avoid repeating myself (DRY)?
– Yes
• Is it self documenting?
– Yes, it has a set of rules that generally make most documentation unnecessary
• Is it flexible enough to bend to my application needs?
– Yes
• Do other people use it?
– Good gosh yes
• Will it work with my database?
– Yes
• Is it still going to be around in X years?
– Ruby has Rails
– Python has Django
– Groovy has Grails
– C# has MVC
– PHP has fragmented framework Hell (aka – who knows?)
– Java has a few major players (Struts 2, Play, etc)

3. Request Flow

4. Rack
Watch this excellent walkthrough of Rack
Middleware:
http://railscasts.com/episodes/151-rack-
middleware
Summary:
It’s a layer of ruby code that passes requests into your app and
sends responses back out. You can add layers to do pre/post
processing on all requests prior to beginning ANY of your
application code.

5. Before the Request
• Configuration
• Initializers
• Gems
• Environments
• Asset Pipeline

6. Models / ActiveRecord
class Post < ActiveRecord::Base
belongs_to :category
has_many :tags, through: :posts_tags
validates :title, presence: true
before_save :create_slug, only: :create
scope :newest_first, order(‘created_at DESC’)
scope :active, where(‘active = ?’,true)
scope :newest_active, newest_first.active
scope :search, lambda do |text|
where(‘title LIKE ?’,”%#{text}%”)
end
def create_slug
self.slug = title.downcase.squish.sub(‘ ‘,’-’)
end
end
post = Post.new(title: ‘Some title’)
post.save!
OR
post = Post.create(title: ‘Some title’)
post.slug # some-title
post.id # 1
post.created_at # Created datetime
post.updated_at # Updated datetime
post.title = ‘New title’
post.save!
# Relations
post.tags.first
post.tags.count
post.category.name
post = Post.include(:tags) # Eager load
post =
Post.search(‘some’).newest_active.first

7. Migrations
class CreateInitialTables < ActiveRecord::Migration
def up
create_table :posts do |t|
t.string :title
t.text :body
t.string :slug
t.integer :category_id
t.timestamps
end
# … create more tables…
add_index :tags, [:name,:something], unique: true
execute “UPDATE posts SET field = ‘value’ WHERE stuff = ‘happens’”
end
def down
drop_table :posts
end
def change
add_column :posts, :user_id, :integer
end
end
$ rake db:migrate

8. Controllers and REST
Class PostsController < ApplicationController
before_filter :authenticate, only: :destroy
def index # GET /posts
end
def new # GET /posts/new
end
def create # POST /posts
end
def show # GET /posts/:id
end
def edit # GET /posts/:id/edit
end
def update # PUT /posts/:id
end
def destroy # DELETE /posts/:id
end
end
# Routes
resources :posts
OR limit it
resources :posts, only: [:create,:new]

9. Views
/app/views
/layouts
/application.html.erb
/posts
/new.html.slim
/new.json.rabl
/index.xml.erb
/_widget.html.erb
# slim example
.post
h2=post.title
.body.grid-8=post.body
# erb example
<div class=“post”>
<h2><%=post.title%></h2>
<div class=“body grid-8”>
<%=post.body%>
</div>
</div>

10. Generators
• rails new .
• rails g scaffold article name content:text
published_on:date

11. LET’S WRITE SOME CODE!