Rails Basics « »

June 4, 2015

$ rails new hello
$ bundle install
$ rails server

$ rails generate controller salutation

create app/controllers/salutation_controller.rb
create app/views/salutation
create test/functional/salutation_controller_test.rb
create app/helpers/salutation_helper.rb
create test/unit/helpers/salutation_helper_test.rb

creates:

controller
helper
view
javascript
stylesheet

Create a view

app/views/salutation/hello.html.erb

Route

config.routes.rb

Hello::Application.routes.draw do
	get ':controller(/:action(/:id(.:format)))'
end

About the Folder Structure

app All the components of your application.
bin Executables to support Rails.
config Configuration files for all of the components of your application.
config.ru A file used by rack servers to start the application.
db Files related to the database you’re using, and a folder for migrations.
Gemfile Used by the bundler gem to keep a list of gems used in your application.
Gemfile.lock Canonical resource of what gems should be installed.
lib Libraries that may be used in your application.
log Log files that your application may require.
public Static assets served by your application, such as images, JavaScript, and CSS files.
Rakefile Lists available for tasks used by Rake.
README.rdoc Human readable file generated to describe an application.
test Directory containing test unit tests for your application.
tmp Contains temporary files supporting your application.
vendor External libraries, such as gems and plug-ins, that your application bundles.

Config Database

config/database.yml

Creating Proejct Databases Rake

$ rake db:create

database migrations
tests
updating Rails support files

For a list of all available Rake tasks.

$ rake -T

Create all the db for all the environments

$ rake db:create:all

dbconsole

$ rails dbconsole

$ .exit

$ rake db:migrate

Creating a Model

Model names are camel-cased singular and correspond to lower-cased plural table names e.g. Article expected a table named articles.

$ rails generate model Article

article model
article test
articles fixture
migration

class CreateArticles < ActiveRecord::Migration
  def change
    create_table :articles do |t|
    	t.string :tible
    	t.text :body
    	t.datetime :published_at
      t.timestamps null: false
    end
  end
end

$ rake db:migrate

Scaffolding

The scaffold provides methods and pages that allow you to insert, update, and delete records in your databse.

$ rails generate scaffold Article title:string body:text published_at:datetime --skip-migration

Adding fields

$ rails generate migration add_excerpt_and_location_to_articles excerpt:string location:string

$ rails generate scaffold Article title:string location:string excerpt:string body:text published_at:datetime --skip-migration

Interatctive Interpreter

$ irb

Ruby Data Types

Strings

String interpolation

"Now is #{Time.now}"

Methods

"Toronto - Canada".downcase
"New York, USA".upcase
"a " + "b"
"HELLO".capitalize
"whatever".methods

Numbers

Fixnum
Bignum
Float

Symbols

:my_symbol

Arrays and Hashes

Arrays

city_array = ['Toronto,'Miami','Paris]
city_array[0]
city_array[1] = 'New York'
city_array << 'London'
city_array + ["Los Angeles"]

Hashes

my_hash = {:canada => "Toronto", :france => "Paris", :uk => "London"}
my_hash[:uk]
my_hash[:canada] = 'Calgary'
my_hash.first
my_hask.keys

Language Basics

Variables

@@count class variables
@name instance variable
SERVER_IP constant
my_string local variables

Operators

assignment [] []=
arithmetic * / % + **
comparision
range .. …
bitwise & ^
logical && not or and

Blocks Iterators

5.times {puts "Hello"}

[1,2,3,4,5].each { |item| puts item }

["a","b","c"].each_with_index do |item, index|
	puts "Item: #{item}"
	puts "Index: #{index}"
	puts "---"
end

Control Structure

now = Time.now

if now == Time.now
	puts "now is the past"
else
	puts "time has passed"
end



a = 5
b = 10
puts "b is greater than a" if a < b
puts "a is greater than b" unless a < b


a = 5
b = 10

while a < b
	puts "a is #{a}"
	a += 1
end

Methods

def time_as_string
        Time.now.to_s
end

def say_hello_to((name)
        "Hello, #{name}!"
end

Classes and Objects

class Student
        # Setter method for the @first_name
        def first_name=(value)
                @first_name = value
        end

        # Getter method for @first_name
        def first_name
                @first_name
        end

        # setter method for @last_name
        def last_name=(value)
                @last_name = value
        end

        # Getter  method for @last_name
        def last_name
                @last_name
        end

        # returns full name
        def full_name
                last_name + ", " + first_name
        end
end

class Student
        attr_accessor :first_name, :last_name, :id_number

        def full_name
                last_name + ", " + first_name
        end
end

class Team
        attr_accessor :name, :students

        def initialize(name)
                @name = name
                @students = []
        end

        def add_student(id_number, first_name, last_name)
                student = Student.new
                student.id_number = id_number
                student.first_name = first_name
                student.last_name = last_name
                @students << student
        end

        def print_students
                @students.each do |student|
                        puts student.full_name
                 end
        end
end