Truncate string attributes to database limit in Rails

truncatable.rb

# frozen_string_literal: true

# Usage:
# Place it in app/models/concerns dir
#
# Include in class
# class Product < ApplicationRecord
#   include Truncatable
# end
#
# Product.find(123).update(title: 'a' * 100) # title will be truncated to database column limit size

module Truncatable
  extend ActiveSupport::Concern

  OMISSION = '…'

  included do
    before_save :truncate_string_attributes
  end

  private

  def truncate_string_attributes
    self.class.columns.each do |column|
      next unless column.type == :string && column.limit

      truncate_value_for_attribute(name: column.name, limit: column.limit)
    end
  end

  def truncate_value_for_attribute(name:, limit:)
    case (value = self[name])
    when String
      return if value.length < limit

      self[name] = value.truncate(limit, omission: OMISSION)
    when Array
      return if value.all? { |v| v.length < limit }

      self[name] = value.map { |v| v.truncate(limit, omission: OMISSION) }
    end
  end
end