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intro-rails-active-record.md

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Intro to Ruby on Rails

MVC - Model View Controller

View - React, HTML, CSS Model - Database layer Controllers - Switchboard that connects the view and model together

Together - MVC creates a full stack application

Rails is open source and is a server side web application framework

Convention over configuration

"Rails magic" - Rails does some of the heavy lifting

To build a rails app: $ rails new app_name -d postgresql -T

Create a database $ rails db:create

Rails Tour

  • Gemfile
  • MVC
    • app/controllers
    • app/models
    • app/views
  • config/routes
  • db: stands for database
  • README

To run the server: $ rails server or $ rails s

Active Record

  • ORM: Object Relational Mapping (translates Ruby and SQL)

During development - Database lives on your machine Rails app - collection of folders and files that can be accessed on GitHub During production - Database will exist on a separate server

Model

Model class defines the structure of the database

$ rails generate model Schedule day:string date:date event:string

  • To create a table in our database we need to migrate our table

$ rails db:migrate

Schema

  • READ ONLY FILE!!
  • Great reference to check database is setup correctly

Interacting with Data in Rails Console

$ rails c

> Schedule.all 
# => [] Shows all instances in database


# Create
> Schedule.create(day: 'Thursday', date: '2022-10-06', event: 'Office hours')
> Schedule.create(day: 'Thursday', date: '2022-10-06', event: 'White boarding practice')
> Schedule.create(day: 'Friday', date: '2022-10-07', event: 'Week 5 assessment')

> Schedule.all

CRUD

Create: create method passing key value pairs Read:

  • .all returns all instances in the database
  • .first gives the first instance in the database
  • .last gives the last instance
  • .find(1) return the instance based on primary key
  • .where(event: 'Office hours') will find based on key value pair, returns a set of all instances that matches it
> Schedule.where(day: 'Thursday')

Update:

  • Store instance to be updated in variable
> assessments = Schedule.last
> assessments.update(event: 'Super awesome assessment')
> assessments
# show updated event
  • The variable is only available until we exit out of the console. Any modifications to the data itself though will persist.

** The syllabus has a different approach to update that will also work! **

> office_hours = Schedule.find 1
> office_hours.event = 'Super awesome office hours!'
> office_hours.save
> office_hours

Delete:

  • Store instance to be deleted in variable
> white_boarding = Schedule.find(2)
> white_boarding.destroy
> Schedule.all
# shows instance no longer is there