Decimals

controller.rb

params[:foo] = DecimalSupport.parse_model_decimals(params[:foo], Foo)

decimal_support.rb

module DecimalSupport
  def self.parse_model_decimals(hash, model, options = {})
    defaults = I18n.translate(:'number.format', locale: options[:locale], default: {})
    precision_defaults = I18n.translate(:'number.precision.format', locale: options[:locale], default: {})
    defaults = defaults.merge(precision_defaults)
    options = options.reverse_merge(defaults)

    hash.each do |field, value|
      column = model.columns.find {|c| c.name == field.to_s}

      hash[field] = if column.type == :decimal
        self.parse_decimal(value, options)
      else
        value
      end
    end
    hash
  end

  def self.parse_decimal(value, options = {})
    if value.blank?
      "0.0"
    else
      separator_position = value.rindex(options[:separator])

      if separator_position.present?
        int_part = value[0...separator_position]
        frac_part = value[(separator_position+1)..-1]

        int_part.gsub!(options[:delimiter], '')
        [int_part, frac_part].join(".")
      else
        value
      end
    end
  end
end

decimals.rb

ActionView::Helpers::FormBuilder.class_eval do
  include ActionView::Helpers::NumberHelper

  def decimal_number_field(field, options = {})
    value = object.send(field)
    column = object.class.columns.find {|c| c.name == field.to_s}

    new_options = { raise: true }
    new_options[:precision] = column.try(:scale)
    new_options[:separator] = options.delete(:separator)
    new_options[:delimiter] = options.delete(:delimiter)
    new_options[:significant] = options.delete(:significant)
    new_options[:strip_insignificant_zeros] = options.delete(:strip_insignificant_zeros)
    new_options[:raise] = true

    new_options.delete_if {|k,v| v.nil? }

    options[:value] = number_with_precision(value, new_options)
    options[:class] = "#{options[:class]} decimal_number_field"

    text_field(field, options)    
  end
end