A nice way to say if your models are 'live', whatever that means.

is_livable.rb

#
# Setup: 
#   * Put this file in lib
#   * Put `require 'is_livable'` in an initializer
#
# Usage:
#   * Within a class like Post, do something like
#      `is_livable :released_at, status: APPROVED`
#   * Then you can do
#      `Post.live, Post.not_live, Post.first.live?`
#   * Arguments to is_livable can be attribute names, or a hash
#     of an attribute name and the thing that makes it live.
#

module IsLivable
  # Could probably do something to eliminate the db call
  def live?
    self.class.live.where(:id => self.id).first.present?
  end
end

class ActiveRecord::Base
    LIVABLE_TYPES = {
      # MySQL specific, probably need to use something else for postgres, etc.
      datetime: "%s < CURTIME()",
      boolean:  "%s IS TRUE"
    }.freeze

  def self.is_livable(*args)
    class_attribute :live_conditions
    self.live_conditions = args.to_a

    conditions = live_conditions.map do |a|
      if a.is_a?(String) || a.is_a?(Symbol)
        a = a.to_s

        # Try to do string interpolation like "%s < CURTIME()" % "released_at"
        LIVABLE_TYPES[self.columns_hash[a].type].try(:%, a)
      elsif a.is_a?(Hash)
        "#{a.first.first} = '#{a.first.last}'"
      end
    end

    conditions = conditions.reject(&:nil?).join(" AND ")

    scope :live, -> { where(conditions) }
    scope :not_live, -> { where("NOT (#{conditions})") }

    include IsLivable
  end
end