Question

I’m not sure if macro is even the correct term. Basically, I want to be able to configure ActiveRecord columns easily (using the familiar AR syntax) so that before_save they will always be formatted a certain way by calling an instance method.

I’d like to make all of this accessable from a mixin.

For example:

class MyClass < ActiveRecord::Base

  happy_columns :col1, :col2  # I really want this type of convenient syntax


  # dynamically created stuff below from a mixin.
  before_save :make_col1_happy
  before_save :make_col2_happy

  def make_col1_happy; self.col1 += " is happy"; end
  def make_col2_happy; self.col2 += " is happy"; end

end

Answer 1

try to extend ActiveRecord , a.e.

#in lib/happy_columns.rb


module HappyColumns
  def happy_columns(cols)
    cols.each do |c|
     before_filter "make_#{c}_happy".to_sym

     #here you could define your instance methot using define_method
      define_method "make_#{c}_happy" do
        #your code
       end

     end



    include InstanceMethods
  end

  module InstanceMethods
   #here you could define other your instancemethod 


  end
end


ActiveRecord::Base.extend HappyColumns

be sure of include the extensions in your load path , then you could use happy_cols in your model.

sorry if there is some mistake , for define_method look at this .

hope this could help.