SQL CRUD

app.rb

# Gem/Library to allow Ruby to interact with the DB
require 'sqlite3'
require 'byebug'

require_relative 'doctor'

# Create a DB connection
DB = SQLite3::Database.new("doctors.db")

#[[1, "John Smith", 39, "Anesthesiologist"], [2, "Emma Reale", 31, "Cardiologist"]]
# We want our individual records/rows to be Hashes
DB.results_as_hash = true

# Let's create an instance of Doctor
# with the first row: id = 1
row = DB.execute("SELECT * FROM doctors WHERE id = 1")
        .first
# Our Doctor initiaze expects hash with symbol keys
# Convert keys to symbols
attrs = row.transform_keys(&:to_sym)

# Create a Doctor instance
doctor = Doctor.new(attrs)
p doctor

# Let's read all instances of Doctor
doctors = Doctor.all
p doctors
p doctors.first.name

# Let's read Doctor with id 2
doctor = Doctor.find(2)
puts "My name is #{doctor.name}"

# Let's create a new Doctor
doctor = Doctor.create(name: "Foo", age: 45)

# ActiveRecord => on Moday/Tuesday
# Doctor.where(id: ids).find_each(&:destroy)
# Doctor.destroy_all

# doctor.update
# doctor.delete
puts "Done!"

doctor.rb

# MVC - M model

# Given a DB row
# attrs = {"id"=>1, "name"=>"John Smith", "age"=>39, "specialty"=>"Anesthesiologist"}
# Doctir.new(attrs)
class Doctor
  attr_accessor :id, :name, :age, :specialty

  def initialize(attributes = {})
    @id = attributes[:id]
    @name = attributes[:name]
    @age = attributes[:age]
    @specialty = attributes[:specialty]
  end

  # Class methods:
  # Doctor.all => return all instances of Doctor
  def self.all
    # rows is an Array of hashes with Doctor data form the DB
    rows = DB.execute("SELECT * FROM doctors")

    # Converts rows to an array of Doctor instances
    rows.map do |row|
      # Convert string keys to symbol keys
      attrs = row.transform_keys(&:to_sym)
      # Doctor.new(attrs) => won't work
      # self.new(attrs) => self is Doctor
      new(attrs)
    end
  end

  def self.find(id)
    row = DB.execute("SELECT * FROM doctors WHERE id = #{id}")
            .first

    # convert string keys to symbol keys
    attrs = row.transform_keys(&:to_sym)

    # Doctor.new(attrs) => won't work
    # self.new(attrs) => self is Doctor
    new(attrs)
  end

  # Doctor.create(name: "Doogie Houser", age: 18)
  def self.create(attributes = {})
    doctor = new(attributes)
    doctor.save
  end

  # Update the instance varitable
  # Also save it to the DB
  def update(attributes = {})
    @name = attributes[:name] || @name
    @age = attributes[:age] || @age
    @specialty = attributes[:specialty] || @specialty
    save
  end

  def save
    if @id.nil?
      # create
    else
      # update
    end
  end
end