Retrospring/app/models/theme.rb

class Theme < ActiveRecord::Base
  include ThemeHelper

  belongs_to :user

  validates_numericality_of :primary_color, :primary_text,
    :danger_color, :danger_text,
    :success_color, :success_text,
    :warning_color, :warning_text,
    :info_color, :info_text,
    :default_color, :default_text,
    :panel_color, :panel_text,
    :link_color, :background_color,
    :background_text, :background_muted,
    greater_than_or_equal_to: 0, less_than_or_equal_to: 0xFFFFFF,
    allow_nil: true, only_integer: true

  has_attached_file :css, use_timestamp: false, s3_headers: {
    'Content-Type' => 'text/css'
  }, fog_file: {
    content_type: 'text/css'
  }
  validates_attachment_content_type :css, content_type: /^text\//

  before_save do
    self.css = nil

    style = ThemeIO.new(render_theme_with_context(self))

    style.instance_variable_set '@content_type', 'text/css'

    self.css = style

    self.css.instance_write :content_type, 'text/css'
    self.css_content_type = 'text/css'
  end
end