ORM Breakout Notes

employee.rb

class Employee < ActiveRecord::Base
  BILLABLE_HOURS = 1950

  belongs_to :store

  validates :first_name, :last_name,
    presence: true

  after_create :increment_employees_count
  after_destroy :decrement_employees_count

  def increment_employees_count
    if gender == "F"
      store.female_employees += 1
    elsif gender == "M"
      store.male_employees += 1
    end
    # store.female_employees += 1 if gender == "F"
    # store.male_employees += 1 if gender == "M"
    store.save # unless gender.nil? # you can add it to skip save sometimes
  end

  def decrement_employees_count
    if gender == "F"
      store.female_employees -= 1
    elsif gender == "M"
      store.male_employees -= 1
    end
    store.save # unless gender.nil? # you can add it to skip save sometimes
  end

  def annual_salary
    hourly_rate * BILLABLE_HOURS
  end

  class << self

    def average_hourly_rate_for(gender)
      # approach 1
      if gender
        where(gender: gender).average(:hourly_rate).round(2)
      else
        average(:hourly_rate).round(2)
      end

      # approach 2
      # return average(:hourly_rate).round(2) if gender.nil?
      # where(gender: gender).average(:hourly_rate).round(2)

      # approach 3
      # gender = gender.nil? ? ["M", "F"] : [gender]
      # where(gender: gender).average(:hourly_rate).round(2)
    end

  end

end

store.rb

class Store < ActiveRecord::Base
  has_many :employees

  validates :name,
    presence: true,
    length: { maximum: 25 }

  validates :annual_revenue,
    numericality: { greater_than_or_equal_to: 0 }

  validates :male_employees, :female_employees,
    numericality: { greater_than_or_equal_to: 0, only_integer: true }

  def annual_expense
    # AR style of doing things
    employees.sum(:hourly_rate) * Employee::BILLABLE_HOURS

    # doing it with inject
    # employees.inject(0){|current_sum, current_employee|
    #   current_sum += current_employee.annual_salary
    # }
  end

  def annual_profit
    annual_revenue - annual_expense
  end

end