Example code: The "Item" model from www.speedie.equipment

item.rb

class Item < ApplicationRecord
  belongs_to :item_type
  belongs_to :location
  delegate :campus, to: :location
  has_many :item_comments, dependent: :destroy
  has_many :service_events, dependent: :destroy
  has_one :last_service_event, -> { order(service_date: :desc, created_at: :desc) }, class_name: "ServiceEvent"
  has_many :calibration_events, dependent: :destroy
  has_one :last_calibration_event, -> { order(date_performed: :desc, created_at: :desc) }, class_name: "CalibrationEvent"
  has_many :location_changes, dependent: :destroy
  has_one :last_location_change, -> { order(date_of_change: :desc, created_at: :desc) }, class_name: "LocationChange"
  # kaminari gem paginates search results - 10 items per page
  paginates_per 10
  # Disallow duplicate serial_numbers
  validates :serial_number, uniqueness: true, allow_blank: true
  # Look into whether I need to cleanup old, uneeded
  # paper_trail version records to avoid clutter
  has_paper_trail

  # If item is edited and location_id is changed in the edit, this hook saves the info
  # to create a location_change record, unless the change in location_id comes directly
  # from a location_change record creation
  after_save :store_location_change, if: :location_id_changed?, unless: :skip_location_change_create
  # skip_location_change_create is set to 'true' in location_changes_controller after
  # creation of a new location_change record to avoid duplicating/overwriting upon item.save
  attr_accessor :skip_location_change_create

  # DO NOT add things to the middle of an enum list, only to the end;
  # adding to the middle would change the array value of each option which
  # would change the value of any option after it in the list on all items
  # QUESTION: Should these values be enum'd on item_type instead of here???
    enum sieve_type: ['Fine', 'Coarse']

    enum fine_sieve_opening_size: ['#400', '#325', '#270', '#200', '#150', '#140', '#120', '#100',
                                   '#80', '#60', '#50', '#45', '#40', '#35', '#30', '#25', '#20',
                                   '#18', '#16', '#14', '#12', '#10', '#8', '#7', '#6'
                                  ]

    enum coarse_sieve_opening_size: ['4"', '3"', '2 1/2"', '2"', '1 3/4"', '1 1/2"', '1 1/4"',
                                     '1"', '7/8"', '3/4"', '5/8"', '1/2"', '7/16"', '3/8"',
                                     '5/16"', '1/4"', '1/8"', '0.265"', '#4'
                                    ]

    enum sieve_diameter: ['18 inch', '12 inch', '8 inch', '3 inch', 'Gilson']

    enum flask_type: ['Rice', 'SpG', 'Other']

    enum volume: ['10ml', '24ml', '25ml', '100ml', '250ml', '400ml', '450ml', '500ml', '1000ml', '2000ml', '4000ml']

    enum caliper_type: ['Axial', 'Digital', 'Dial', 'Proportional']

    enum caliper_size: ['(12")', '(6")']

    enum gauge_type: ['(Digital)', '(Dial)']

    enum thermometer_type: ['Mercury', 'PRT', 'Thermistor', 'Thermocouple', 'Infrared', 'Pocket']

    enum scale_resolution: ['1kg', '5g', '1g', '0.5g', '0.1g', '0.01g', '0.001g']

    enum scale_range: ['300lb', '110lb', '20kg', '15kg', '12kg', '500g', '200g', '220lb', '1000g']

    enum groove_tool_type: ['AASHTO', 'ASTM']

    enum operation_type: ['Manual', 'Automatic']

    enum marshall_compaction_pedestal_number: ['Single', 'Double']

    enum proctor_mold_type: ['Solid', 'Split']

    enum proctor_mold_six_types: ['(Solid)', '(Split)']

    enum proctor_hammer_weight: ['5.5lb', '10lb']

    enum capping_mold_size: ['2x4', '4x8', '6x12']

    enum saw_type: ['Chop', 'Lapidary', 'Tile', 'Wet']

    enum penetrometer_type: ['Cone', 'Acme', 'Concrete', 'Soil']
  
 
  # Items index "Item Type" filter
  scope :in_type, -> (type_name) { joins(:item_type).where(types: { name: type_name }) }
 
  # Items index "In Service Only" filter
  scope :in_service, -> { joins(:last_service_event).where(service_events: { status: ServiceEvent.statuses[:in_service] }) }
  
  # Campus index filter
  scope :at_campus, -> (campus_name) { joins(:campus).where(campuses: { name: campus_name }) }
  
  
  # Fix this scope to filter calibrations due soon
  # scope :calibration_due_soon, -> { joins(:last_calibration_event).where(calibration_events: { :date_performed... }) }

  # Items index search query
  scope :search, -> (query) { joins(:item_type, location: :campus)
                              .where("cast(items.id as text) ILIKE ? 
                                     OR serial_number ILIKE ? 
                                     OR manufacturer ILIKE ? 
                                     OR model ILIKE ? 
                                     OR items.notes ILIKE ? 
                                     OR item_types.name ILIKE ? 
                                     OR locations.name ILIKE ? 
                                     OR campuses.name ILIKE ?", 
                                     "#{query}",
                                     "#{query}%",
                                     "#{query}%",
                                     "#{query}%",
                                     "%#{query}%",
                                     "%#{query}%",
                                     "%#{query}%",
                                     "%#{query}%"
                                    )
                              }

  # Conversions for purchase_cost to display as currency
  # (had to work around number_field limitations)
  def purchase_cost
    purchase_cost_in_cents.to_f / 100
  end

  def purchase_cost=(value)
    value = value.to_f * 100
    self.purchase_cost_in_cents = value
  end

  # When location_id of item is changed via the edit form, store
  # location change info so that a location_change record can be created
  def store_location_change
    location_changes.create(location_id: location_id, date_of_change: DateTime.now.to_date)
  end

  # Check for presence of item_type variables for helper in the view
  def has_item_type_variables
    if
      self.sieve_type?                          ||
      self.sieve_diameter?                      ||
      self.flask_type?                          ||
      self.volume?                              ||
      self.caliper_type?                        ||
      self.caliper_size?                        ||
      self.gauge_type?                          ||
      self.thermometer_type?                    ||
      self.scale_resolution?                    ||
      self.scale_range?                         ||
      self.groove_tool_type?                    ||
      self.operation_type?                      ||
      self.marshall_compaction_pedestal_number? ||
      self.proctor_mold_type?                   ||
      self.proctor_mold_six_type?               ||
      self.proctor_hammer_weight?               ||
      self.capping_mold_size?                   ||
      self.saw_type?                            ||
      self.penetrometer_type? 
      true
    else
      false
    end
  end

end