Ruby-on-rails – Ruby mixins and calling super methods

rubyruby-on-rails

Ok, so I've been refactoring my code in my little Rails app in an effort to remove duplication, and in general make my life easier (as I like an easy life). Part of this refactoring, has been to move code that's common to two of my models to a module that I can include where I need it.

So far, so good. Looks like it's going to work out, but I've just hit a problem that I'm not sure how to get around. The module (which I've called sendable), is just going to be the code that handles faxing, e-mailing, or printing a PDF of the document. So, for example, I have a purchase order, and I have Internal Sales Orders (imaginatively abbreviated to ISO).

The problem I've struck, is that I want some variables initialised (initialized for people who don't spell correctly 😛 ) after the object is loaded, so I've been using the after_initialize hook. No problem… until I start adding some more mixins.

The problem I have, is that I can have an after_initialize in any one of my mixins, so I need to include a super call at the start to make sure the other mixin after_initialize calls get called. Which is great, until I end up calling super and I get an error because there is no super to call.

Here's a little example, in case I haven't been confusing enough:

class Iso < ActiveRecord::Base
  include Shared::TracksSerialNumberExtension
  include Shared::OrderLines
  extend  Shared::Filtered
  include Sendable::Model

  validates_presence_of   :customer
  validates_associated    :lines

  owned_by                :customer
  order_lines             :despatched # Mixin

  tracks_serial_numbers   :items  # Mixin

  sendable :customer                      # Mixin

  attr_accessor :address

  def initialize( params = nil )
    super
    self.created_at ||= Time.now.to_date
  end
end

So, if each one of the mixins have an after_initialize call, with a super call, how can I stop that last super call from raising the error? How can I test that the super method exists before I call it?

Best Answer

You can use this:

super if defined?(super)

Here is an example:

class A
end

class B < A
  def t
    super if defined?(super)
    puts "Hi from B"
  end
end

B.new.t
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