FactoryGirl model generator to support automatically add columns

factory_girl_model_generator_decorator.rb

# generate factory with columns for model
#
# $ bundle exec rails g factory_girl:model User

require 'factory_girl'
require 'generators/factory_girl/model/model_generator'

FactoryGirl::Generators::ModelGenerator.class_eval do
  alias :command_line_attributes :attributes

  def attributes
    if command_line_attributes.present?
      command_line_attributes
    else
      # TODO: handle the situation when the model or corresponding table doesn't exist yet
      columns = name.constantize.columns
      columns.map do |column|
        "#{column.name}:#{column.type}"
      end
    end
  end
end