Custom Active Storage Validator

attached_validator.rb

class AttachedValidator < ActiveModel::EachValidator
  # Active Storage validator to ensure that an attachment is attached.
  #
  # usage:
  #   validates :upload, attached: true
  #
  def validate_each(record, attribute, _value)
    return if record.send(attribute).attached?

    errors_options = {}
    errors_options[:message] = options[:message] if options[:message].present?

    record.errors.add(attribute, :blank, **errors_options)
  end
end

size_validator.rb

# Source: https://github.com/igorkasyanchuk/active_storage_validations
# Example usage:
# validates :preview, attached: true, size: { less_than: 100.megabytes , message: 'is not given between size' }
class SizeValidator < ActiveModel::EachValidator # :nodoc:
  delegate :number_to_human_size, to: ActiveSupport::NumberHelper

  AVAILABLE_CHECKS = %i[less_than less_than_or_equal_to greater_than greater_than_or_equal_to between].freeze

  def check_validity!
    return true if AVAILABLE_CHECKS.any? { |argument| options.key?(argument) }

    raise ArgumentError, "You must pass either :less_than, :greater_than, or :between to the validator"
  end

  def validate_each(record, attribute, _value)
    # only attached
    return true unless record.send(attribute).attached?

    files = Array.wrap(record.send(attribute))

    errors_options = {}
    errors_options[:message] = options[:message] if options[:message].present?

    files.each do |file|
      next if content_size_valid?(file.blob.byte_size)

      errors_options[:file_size] = number_to_human_size(file.blob.byte_size)
      errors_options[:min_size] = number_to_human_size(min_size)
      errors_options[:max_size] = number_to_human_size(max_size)

      record.errors.add(attribute, :file_size_out_of_range, **errors_options)
      break
    end
  end

  def content_size_valid?(file_size)
    if options[:between].present?
      options[:between].include?(file_size)
    elsif options[:less_than].present?
      file_size < options[:less_than]
    elsif options[:less_than_or_equal_to].present?
      file_size <= options[:less_than_or_equal_to]
    elsif options[:greater_than].present?
      file_size > options[:greater_than]
    elsif options[:greater_than_or_equal_to].present?
      file_size >= options[:greater_than_or_equal_to]
    end
  end

  def min_size
    options[:between]&.min || options[:greater_than] || options[:greater_than_or_equal_to]
  end

  def max_size
    options[:between]&.max || options[:less_than] || options[:less_than_or_equal_to]
  end
end