Generating methods that update an instance or multiple database records the same way

membership.rb

class Membership

  ###### SCOPES ######
  
  scope :active,        where(:is_active => true)
  scope :not_active,    where{is_active != true}
  scope :removed,       where(:is_active => false, :unsubscribed_at => nil)
  scope :unsubscribed,  where{(is_active == false) & (unsubscribed_at != nil)}
  scope :admin,         active.where(:is_admin => true)
  
  ####################
  
  STATE_UPDATES = {
    :activate     => { :attributes => ->{{:is_active => true}}, :if => ->{{:is_active => false}} },
    :remove       => { :attributes => ->{{:is_active => false}}, :if => ->{{:is_active => true}} },
    :restore      => { :attributes => ->{{:is_active => true}}, :if => ->{{:is_active => false, :unsubscribed_at => nil}} },
    :unsubscribe  => { :attributes => ->{{:is_active => false, :unsubscribed_at => Time.now}}, :if => ->{{:is_active => true}} }
  }
  
  STATE_UPDATES.each do |name, config|
    # create method that changes state
    define_method name do
      # if the instance matches the attribute values, it can be updated with the new values
      result = config[:if].call.map{|k,v| send(k) == v}.all?
      # update the instance with the new values if the old values were correct
      self.attributes = config[:attributes].call, {:without_protection => true} if result
      # indicate if a change was possible
      result
    end
    
    # create method that auto-saves
    define_method :"#{name}!" do
      send(name)
      save!
    end
    
    # create method that mass updates db with state change
    define_singleton_method :"#{name}!" do
      scoped.where(config[:if].call).update_all(config[:attributes].call)
    end
  end
  
  ##### OLD WAY THAT IS REPLACED BY GENERATED METHODS ABOVE #####
  
  def activate
    if !active?
      self.is_active = true
      true
    else
      false
    end
  end
  
  def activate!
    activate
    save!
  end
  
  # update for a collection
  def self.activate!
    scoped.not_active.update_all(:is_active => true) > 0
  end
  
  def active?
    is_active == true
  end

end