ruby_and_rails_best_practices.md

• Memoization
  • Parametric memoization (using the special Hash constructor):

  Hash.new {|h, key| h[key] = some_calculated_value }

  class City < ActiveRecord::Base
    def self.top_cities(order_by)
      @top_cities ||= Hash.new do |h, key|
        h[key] = where(top_city: true).order(key).to_a
      end
      @top_cities[order_by]
    end
  end

  • Memoizing false or nil values:

  def has_keys?
    return @has_keys if defined? @has_keys
  
    @has_keys = some_logic_here
  end

• Concerns, service objects, and tableless models