Creates :meta from given :body when saving models

metable_model.rb

# app/models/concerns/metable_model.rb
#
# https://gist.github.com/firedev/644b41967cf6c1c9d035
#
# Usage:
#
# rails g migration addMetaToModel meta:string
#
# include MetableModel
# metable [:meta] [, :body] [, &block]
#
# Creates :meta from given :body when saving models if no :meta given
# Truncates first line up to the 160 chars/first full stop whichever comes first
# or runs :body through a &block:
#
# include MetableModel
# metable
#
# or you can pass a block with your own handler:
# metable(:meta) { |body| body.truncate(100) }
#

module MetableModel
  extend ActiveSupport::Concern

  module ClassMethods
    def metable(meta_attr = :meta, body_attr = :body, &block)
      before_validation { create_meta(body_attr, meta_attr, &block) }
      # validates meta_attr, presence: true
    end
  end

  def create_meta(body_attr, meta_attr, &block)
    return if send(body_attr).blank? || send(meta_attr).present?
    send "#{meta_attr}=", create_meta_from(body_attr, &block)
  end

  def create_meta_from(body_attr, &_block)
    if block_given?
      yield send(body_attr).to_s
    else
      send(body_attr).to_s
                     .split("\n")[0]
                     .to_s.split('.')[0]
                     .to_s
                     .truncate(160, separator: '.')
    end
  end
end