Ruby notes

07 February 2017

  • rails
  • ruby
DESCRIPTION: This is a collection of notes while learning Ruby

TAKE NOTE: Everything in Ruby is an object

Its documentation is found here:

Ruby is probably best known for the Ruby on Rails framework. The documentation for this can be found here:


Ruby Class documentation

Naming: all class names should begin with a capital letter.

Creating an object: you call your object outside of the object with This creates a new instance of the object.


Ruby attr_accessor documentation

When you want to read/write to the database, in the Class you would need to write two read/write methods:

class Person
  #read accessor
  def name
  #write accessor
  def name=(str)
    @name = str

person = = 'Sam' # => "Sam"

a shortcut to this using accessor is:

class Person
  attr_reader :name
  attr_writer :name

This can then be shortened down further to:

class Person
  attr_accessor :name


Rails Model documentation

Models are where we determine database table relationships and filters/validations to any data being saved to the database.

Database Relationships

Rails Active Record documentation

SQL databases are relational and we must determine the relationship between the data sets.

The types of relationships are as follows:

By simply writing one of the three lines above in the model for a dataset, we determine the relationship.

For example. If we have two databases, one for a persons belongings, and one for persons. We might have two models as follows:

class Person < ActiveRecord::Base
  one_to_many :belonging
class Belonging < ActiveRecord::Base
  belongs_to :person

You will see above I used a belongs_to relationship. This is called a join query. There are a number of join queries:



Rails Active Record Validations documentation

In the models directory, you can add in validations for data that is going to be added to your directory to ensure your database is clean data added that you approve of.

class Person < ApplicationRecord
  validates :status,
            presence: true,
            length: { minimum: 3, maximum: 1000 },
            uniqueness: true,
            numericality: true,
            format: { with: /.*/ },
            acceptance: true,
            confirmation: true


Rails Action Controller documentation

Controllers are the brains of the website. The controller accesses the model to input/output data. In addition it retrieves the data that is to be shown in the HTML.

The different routes in the application are as follows:

HTTP Verb Path Controller#Action Used for
GET /photos photos#index display a list of all photos
GET /photos/new photos#new return an HTML form for creating a new photo
POST /photos photos#creates create a new photo
GET /photos/:id photos#show display a specific photo
GET /photos/:id/edit photos#edit return an HTML form for editing a photo
PATCH/PUT /photos/:id photos#update update a specific photo
DELETE /photos/:id photos#destroy delete a specific photo

At the bottom of the controller there should be a method called version_params. This determines which methods are allowed to be run in the controller. If for example you do not want a rogue piece of data being saved to the database, this can stop that.

def version_params
  params.require(:photos).permit(:photo_id, :photo_date, :photo_commentary)


Rails Routes documentation

This is the section of the Rails app which controls how the URL is routed to the correct controller action. For our photo rails App a standard route page would look something like this:

MyRailsPhotoApp::Applcation.routes.draw do

  # The root url to the webpage will direct to the photos controller Index action
  root 'photos#index'

  # Gives the application access to the photos controller
  resources :photos

  # Direct the url /photos to the photos controller index action
  get '/photos' => 'photos#index'

  # Redirect a custom url '/newphoto' to the photos controller new action
  get '/newphoto' => redirect('photos#new')

  # Create a filtered index. e.g. if you direct to the URL /photos/sam this would filter the index page to an index of just my photos.
  get '/photos/:name', to: 'photos#index', as: 'myphotos'


There is a lot more filtering that can be done within the controller to tailor what gets fed through to the view.