Crazy initializer - good for one-off Rails apps

easy.rb

# Add this file to your config/initializers directory.
#
# Then you can do things like:
#
#   Product[5]          instead of Product.find_by(id: 5)
#   Product.sample      to pull a random Product row
#   Product.sample(3)   to pull three random Product rows (but they will be consecutive)
#
# Biggest part: automatic associations!  
#
# Normal belongs_to/has_many will "just work" based on foreign key detection.
# You will need to add any has_many :through associations yourself.
# 
# Finally, the stupid "You must establish a connection" in Rails console has been silenced.

class ActiveRecord::Base

  def self.sample(n = 1)
    n = [[n.to_i, 1].max, count].min  # guard against invalid sample size
    offset(rand(count - n)).first(n)
  end

  def self.[](id)
    find_by_id(id)
  end

end

module EZ
  class AssociationInjector

    def models
      @models ||= begin
        tables = ActiveRecord::Base.connection.tables - ["schema_migrations"]
        models = tables.map { |t| t.classify.constantize }
      end
    end

    def inject_associations
      models.each do |model|
        inject_association_for model
      end
    end

    def inject_association_for(model)
      model.column_names.grep(/_id$/).each do |foreign_key_column|
        bt_model_class = add_belongs_to(model, foreign_key_column.chomp("_id"))
        add_has_many model, bt_model_class
      end
    end

    def add_belongs_to(model, bt_name)
      return if model.reflections.keys.include?(bt_name)

      bt_model_class = bt_name.classify.constantize
      return if !models.include?(bt_model_class)

      model.class_eval do
        belongs_to bt_name.to_sym
      end

      return bt_model_class
    end

    def add_has_many(model, bt_model_class)
      hm_name = model.name.underscore.pluralize
      if !bt_model_class.reflections.keys.include?(hm_name)
        bt_model_class.class_eval do
          has_many hm_name.to_sym, dependent: :destroy
        end
      end
    end
  end

end

ActiveRecord::Base.connection  # avoid silly warning in rails console
EZ::AssociationInjector.new.inject_associations