Monkey Patches

If you're using a Solidus version minor than 3.2, the content on this page is still applicable. However, you might want to look at the previously recommended approach through decorators .

You can take advantage of Ruby's meta-programming features to monkey patch Solidus functionality for your store.

As the first thing, you need to configure a directory where you'll place your custom code. For instance, app/overrides/:

    
      module MyStore
  class Application < Rails::Application
    # ...
    overrides = "#{Rails.root}/app/overrides"
    Rails.autoloaders.main.ignore(overrides)
    config.to_prepare do
      Dir.glob("#{overrides}/**/*.rb").each do |override|
        load override
      end
    end
  end
end

    
  

If you're using the classic autoloader (the default before Rails 6), you instead need to go with:

config/application.rb

Ruby

    
      module MyStore
  class Application < Rails::Application
    # ...
    config.to_prepare do
      Dir.glob("#{Rails.root}/app/overrides/**/*.rb").each do |override|
        require_dependency override
      end
    end
  end
end

    
  

For example, if you want to add a method to the Spree::Order model, you could create /app/overrides/my_store/order_total_modifier.rb with the following contents:

    
      module MyStore::OrderTotalModifier
  def total
    super + BigDecimal(10.0)
  end

  Spree::Order.prepend self
end

    
  

This creates a new module called MyStore::OrderTotalModifier that prepends its methods early in the method lookup chain. So, for method calls on Spree::Order objects, the monkey patch's total method would override the original total method.

With the code above live on your server, every call to Spree::Order.total will return the original total plus $10 (or whatever your currency is).

Using class-level methods

You'll need to define a special method in order to access some class-level methods

    
      module MyStore::ProductAdditions

  # This is the place to define custom associations, delegations, scopes and
  # other ActiveRecord stuff
  def self.prepended(base)
    base.has_many :comments, dependent: :destroy
    base.scope    :sellable, -> { base.where(...).order(...) }
    base.delegate :something, to: :something
  end

  ...

  Spree::Product.prepend self
end

    
  

In this example, we're extending the functionality of Spree::Product. We include an ActiveRecord association, scope, and delegation.

Monkey patches and Solidus upgrades

Monkey patches can complicate your Solidus upgrades. If you depend on them, ensure that you test them before upgrading in a production environment. Note that Solidus's core classes may change with each release.