Sample model

gas_safety_record.rb

# frozen_string_literal: true

class GasSafetyRecord < ApplicationRecord
  # Associations
  belongs_to :installation_job, inverse_of: :gas_safety_record

  has_many :appliances,
           class_name: "GasSafetyRecordAppliance",
           dependent:  :destroy,
           inverse_of: :gas_safety_record

  accepts_nested_attributes_for :appliances

  # Validations
  validates              :installation_job_id,                presence: true
  validates              :issued_by_license_number,           presence: true
  validates              :boiler_appliance,                   presence: true
  validates_inclusion_of :co_alarm_in_date,                   in: [true, false]
  validates_inclusion_of :co_alarm_present,                   in: [true, false]
  validates_inclusion_of :co_alarm_working,                   in: [true, false]
  validates_inclusion_of :equipotential_bonding_satisfactory, in: [true, false]
  validates_inclusion_of :emergency_control_accessible,       in: [true, false]
  validates_inclusion_of :gas_installation_pipework_safe,     in: [true, false]
  validates_inclusion_of :gas_tightness_test_satisfactory,    in: [true, false]
  validates_inclusion_of :label_in_the_emergency_control,     in: [true, false]
  validates_inclusion_of :received_by_missing,                in: [true, false]
  validates_inclusion_of :smoke_alarm_present,                in: [true, false]
  validates_inclusion_of :smoke_alarm_working,                in: [true, false]
  validate               :received_by_consistency

  # Logging
  add_log_entries_for(
    :create,
    fields: {
      created_at: ->(_record) { "Gas safety record received" }
    },
    to: :installation_job
  )

  # Instance Methods
  delegate :order_short_id,                    to: :installation_job
  delegate :standing_pressure_at_the_meter,    to: :boiler_appliance, allow_nil: true
  delegate :working_pressure_at_the_meter,     to: :boiler_appliance, allow_nil: true
  delegate :working_pressure_at_the_appliance, to: :boiler_appliance, allow_nil: true

  def boiler_appliance
    @_boiler_appliance ||= appliances.select(&:boiler?).detect(&:pressures?)
  end

  def has_defects_remedials_or_advices?
    [defects, remedials].any?(&:present?)
  end

  def most_recent_updated_at
    [updated_at, appliances.map(&:updated_at)].flatten.max
  end

  def pdf_filename
    short_id      = installation_job.order_short_id
    customer_name = installation_job.customer.full_name.parameterize
    timestamp     = most_recent_updated_at.to_s(:db).tr(" ", "_").tr(":", "-")
    "gas-safety-record_#{short_id}_#{customer_name}_#{timestamp}.pdf"
  end

  private

  # Validators
  def received_by_consistency
    errors.add(:received_by_missing, "must be consistent with received_by_* values") unless
    ![
      received_by_name,
      received_by_date,
      received_by_signature,
      received_by_property_relationship
    ].all?(&:present?) == received_by_missing
  end
end