Rails for Beginners - Le Wagon

Alex
Ruby on Rails
for Beginners

Types of Objects
String
Integer
Floats
Array
Hash
“london”
12
3.14
[“london”, “paris”]
{first_name: “alex”, last_name: “benoit"}

cities.each do |city|
# …
end
cities = [“london”, “paris”, “new york”]
cities.length # => 3

class Car
end
car.rb
Car.new
Car.new
Car.new
OOP = Data + Behaviour

users
id username email
1 olivier olivier@kudoz.com
2 edward ed@lovelyhood.com
3 vincent vincent@uslide.io

users products
id username email
id name url user_id
1 LovelyHood lovely-hood.com

users products
id username email
id name url user_id
1 LovelyHood lovely-hood.com 2

users products
id username email
id name url user_id
2 Kudoz getkudoz.com 1
3 uSlide uslide.io 3
4 Freshest frshst.com 2

users products
id username email
id name url user_id
a user has many products
a product belongs to one user
1..N relationship

users products
id username email
id name url user_id
primary key primary key foreign key

History
Created in 2003 by David Heinemeier Hansson (DHH), while working on Basecamp.
Extracted and released it as open source code in July of 2004

Motto
Convention Conﬁgurationover

Ruby community
+100k gems on rubygems.org

Rails new
$ rails new app_name
$ rails new app_name -T --database=postgres

Create the database
$ rails db:create

Launch server
$ rails server
http://localhost:3000

Let’s create the new Rails app!

.
├── app
│ ├──
│ ├──
│ └──
│
└── config
controllers
models
views
└── routes.rb
MVC

config/routes.rb
Router
HTTP
request
MVC

config/routes.rb
Router
app/controllers
Controller
HTTP
request
routed
to controller
MVC

config/routes.rb
Router
app/controllers
Controller
app/models
Model
PostgreSQL 
database
HTTP
request
routed
to controller
Get data
from model
MVC

config/routes.rb
Router
app/controllers
Controller
app/models
Model
app/views
View
PostgreSQL 
database
HTTP
request
routed
to controller
Get data
from model
Inject it
in view
MVC

config/routes.rb
Router
app/controllers
Controller
app/models
Model
app/views
View
PostgreSQL 
database
HTTP
request
routed
to controller
Get data
from model
Inject it
in view
render HTML
MVC

Rails app
config/routes.rb
Router
app/controllers
Controller
app/models
Model
app/views
View
PostgreSQL 
database
1 2
3
4
5

HTTP request?
some link
submit

HTTP basics
A protocol to transfer resources
Based on a system of request / response
Between 2 machines, a client and a server

HTTP request is MORE THAN a URL

HTTP request is 4 things
1 - HTTP verb (GET / POST / PATCH / DELETE)
2 - URL
3 - headers
4 - body (not always)

Rails routing
GET /products
get “home” => “pages#home”
get “about” => “pages#about”
get “products” => “products#index”
post “products” => “products#create”
PagesController
ProductsController
def index
…
end
def create
…
end

PagesController
def home
…
end
def team
…
end
views/pages
home.html.erb
team.html.erb
Action/View convention

ﬁle.html
<h1>…</h1>
< >
+
ﬁle.html.erb
<%= %>
< >
< >
< >
< >
<h1>…</h1>
< >
< >
< >
<%= %>

PagesController
def home
end
pages/home.html.erb
<%= @time %>
<h1>…</h1>
< >
< >
< >
@time = Time.now
Instance variables

Let’s build the pages and product controller!
pages#home pages#about products#index

app/models
Model Database
ActiveRecord

$ rails g model Product name:string

class Product < ActiveRecord::Base
…
end
ActiveRecord Model

class CreateProducts < ActiveRecord::Migration
def change
create_table :products do |t|
t.string :name
t.timestamps null: false
end
end
end
ActiveRecord Migration

$ rails db:migrate
Run Pending Migrations

$ rails console
Play with your Model

All
> Product.all
SELECT * FROM products

New & Save
> kudoz = Product.new(name: “kudoz”, url: “getkudoz.com”)
> kudoz.save
INSERT INTO products (name, url)
VALUES ('kudoz', 'getkudoz.com')

> Product.find(1)
WHERE id = 1
Find

> Product.find_by_name(“kudoz”)
WHERE name = “kudoz”
Find By

Validations
end
presence: true, uniqueness: truevalidates :name,

Associations
end
belongs_to :user

Let’s build our Product Model!

1 - dynamic URL
GET https://www.facebook.com/:user_name
GET https://www.facebook.com/romainpaillard
params[:user_name] => “romainpaillard”

2 - query string
GET https://www.airbnb.com/s/roma?checkin=02/17/2016
params[:checkin] => 02/17/2016

3 - POST request
POST https://www.lewagon/apply
params[:first_name] => “Boris”
{
“first_name": “Boris",
“last_name”:”Paillard"
} } request  
body

Good news !
params
dynamic URL query string POST request body

Let’s build the show view of a product!
products#show

Rails CRUD Routes
We already built index and show actions!

What’s CRUD?
C
Create
R
Read
U
Update
D
Delete

We always need same actions
As a user, I can CRUD a ﬂat
As a user, I can CRUD a tweet
As a user, I can CRUD a post
As a user, I can CRUD a product

get “products” “products#index”=>
get “products/:id” “products#show”=>
get “products/new” “products#new”=>
post “products” “products#create”=>
get “products/:id/edit” “products#edit”=>
patch “products/:id” “products#update”=>
delete “products/:id” “products#destroy”=>

Let’s rebuild our Routes
but this time using resources!

Rails Helpers for Links
<%= link_to “New Product”, new_product_path %>
<a href=“/products/new”>New Product</a>

Let’s put links in our website
links to home, to product index, to product show

Rails CRUD Routes
Let’s build the new and create actions

get “products/new” “products#new”=>
So that user can create new product…
post “products” “products#create”=>
resources :products, only: [:new, :create]

class ProductsController
def new
@product = Product.new
end
def create
…
end
end

<%= form_for @product do |f| %>
<%= f.text_field :name %>
<%= f.text_field :tagline %>
<%= f.submit %>
<% end %>
<form action="/products" method="post">
<input type="text" name="product[name]" id=“product_name”>
<input type="text" name="product[tagline]" id=“product_tagline"> 
<input type="hidden" name="authenticity_token" value=“HJYkH..”> 
<input type="submit">
</form>

params.require(:product).permit(:name, :tagline)
Strong params (whitelisted)

def new
@product = Product.new
end
def create
safe_params = params.require(:product).permit(:name, :tagline)
product = Product.new(safe_params)
product.save 
redirect_to products_path
end
end

Let’s implement those actions
products#new, products#create

Rails CRUD Routes
Let’s build the edit and update actions

get “products/:id/edit” “products#edit”=>
So that user can edit an existing product…
patch “products/:id” “products#update”=>
resources :products, only: [:edit, :update]

def edit
@product = Product.find(params[:id])
end
def update
…
end
end

<%= form_for @product do |f| %>
<%= f.text_field :name %>
<%= f.text_field :tagline %>
<%= f.submit %>
<% end %>
<form action="/products" method="post">
<input type="text" name="product[name]" id=“product_name” value=“Product Hunt”>
<input type="text" name="product[tagline]" id=“product_tagline” value=“Great Website!”> 
<input type="hidden" name="authenticity_token" value=“HJYkH..”> 
<input type="submit">
</form>

params.require(:product).permit(:name, :tagline)
Strong params, again

def edit
@product = Product.find(params[:id])
end
def create
safe_params = params.require(:product).permit(:name, :tagline)
product = Product.find(params[:id])
product.update(safe_params) 
end
end

Let’s implement those actions
products#edit, products#update

Rails CRUD Routes
Let’s build the destroy actions

delete “products/:id” “products#destroy”=>
So that user can delete a product…
resources :products, only: [:destroy]

def destroy
product = Product.find(params[:id])
product.destroy
end
end

Let’s implement that action
products#destroy

Rails for Beginners - Le Wagon

Rails for Beginners - Le Wagon

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