Post-purchase hooks in Spree

Spree is a nifty e-commerce platform on Rails. It’s open-source and fairly easy to customise. In particular, the ordering process uses state_machine which lets you hook in to any part you need to. I’m using Spree v1.2.0, which is the latest version right now.

Adding a post-purchase hook is easy. First you’ll need to have the following in a file in your lib/ folder. I just used lib/spree_site.rb:

Dir.glob(File.join(File.dirname(__FILE__), "../app/**/*_decorator*.rb")) do |c|
  Rails.configuration.cache_classes ? require(c) : load(c)

This tells Spree to look for files named _decorator in your app/ directory and load them in.

Next up we want to override the Order model. Create the file app/models/spree/order_decorator.rb and stick this in:

Spree::Order.class_eval do

  def say_hello
    puts 'Hello!'
    puts "This order cost #{total}"
    # do something interesting, like notify an external webservice about this order

Spree::Order.state_machine.after_transition :to => :complete,
                                            :do => :say_hello

The first part uses Ruby’s classeval to add a new method to the Order model. The second part tells the state machine to run the new ‘sayhello’ method after the :complete (end of checkout) transition occurs.

And that’s all there is to it!

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