demarches-normaliennes/app/models/champs/decimal_number_champ.rb

class Champs::DecimalNumberChamp < Champ
  before_validation :format_value
  validates :value, numericality: {
    allow_nil: true,
    allow_blank: true,
    message: -> (object, _data) {
      "« #{object.libelle} » " + object.errors.generate_message(:value, :not_a_number)
    }
  }

  def for_export
    processed_value
  end

  def for_api
    processed_value
  end

  private

  def format_value
    return if value.blank?

    self.value = value.tr(",", ".")
  end

  def processed_value
    return unless valid_champ_value?

    value&.to_f
  end
end