The boss of metaprogramming

filters.rb

# You know you are the boss, when you take this
  def filter(questions_query)
    filter_categories filter_incomplete questions_query
  end

  def filter_incomplete(query)
    filtering_on?(:incomplete) ? query.incomplete : query
  end
  def filter_categories(query)
    filtering_on?(:categories) ? query.in_categories(*@original_params[:categories]) : query
  end

# and make it so much more glorious with amazing metaprogramming skillz to eliminate all that horrible duplication
  def self.generate_filter(key, if_filtering)
    define_method "filter_#{key}" do |query|
      filtering_on?(key) ? if_filtering.(query, @original_params) : query
    end
  end
  filters = {
    :incomplete => ->(query, original_params) { query.incomplete },
    :categories => ->(query, original_params) { query.in_categories(*original_params[:categories]) }
  }
  filters.each_pair do |key, filter|
    generate_filter key, filter
  end

  class_eval <<LOL
    def filter(questions_query)
      #{filters.keys.map{|f| "filter_#{f}"}.join(" ")} questions_query
    end
LOL

# Now I can add new filters by adding the filter hash! AMAZEBALLS! NO MORE DUPLICATION!!!!

I don't understand what lines 2-11 do. I'm glad you ameliorated it.

I know, right. I'm a firm believer in intention-revealing coding, as well as eliminating duplication. It is a fine line, but my many years of programming help me navigate that line. Clearly the second form solves a lot of the readability problems of the first form.