active-record-intro.md

ACTIVE RECORD

• ORM - object relational mapping
• Translator
• translating Ruby to SQL

MODEL - works with db

rails generate model Dog name:string breed:string age:integer

Dog - class, must be singular and PascalCase followed by column_name:datatype no spaces between column_name & datatype! no commas between columns

• rails new active_record_intro -d postgresql -T
• cd active_record_intro
• rails db:create
• rails generate model Animal category:string name:string age:integer
• rails db:migrate --> creates the schema: db/schema

ActiveRecord::Schema[7.1].define(version: 2024_03_13_175352) do
  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "animals", force: :cascade do |t|
    t.string "category"
    t.string "name"
    t.integer "age"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

end

Remember CRUD - Create, Read, Update, Delete

rails c or rails console

Animal.all --> [] returns empty array because no data yet, but shows the table exists!

Create

Animal.create(category:"giraffe", name:"jeffrey", age:35) Animal.create(category:"shark", name:"shemu", age:210)

Read

Animal.all Animal.first Animal.second Animal.find(1) find by primary Key Animal.where(age: 210)

Update

animal_1 = Animal.find(1) animal_1.update(name:"Mike")

Animal.first.update(name:"Tobey")

Delete

second = Animal.second second.destroy