Defining the same class twice in Ruby

The following code works but I don't understand why. I have two files. The first is a class called walmart.rb located at active_market/walmart.rb. Here is the class definition:

module ActiveMarket
    class Walmart
        def test_one
            puts "test one"
        end
    end
end

For my Walmart class I have "API implementations" for Walmart APIs such as Order, Fulfillment, Report, etc. So I created a folder and another class for my first API implementation at active_market/walmart/order.rb.

Here is the Order class definition:

class ActiveMarket::Walmart
  def test_two
    puts "test two"
  end

  class Order < ActiveMarket::Walmart
    def test_all
      test_two
      test_one
    end
  end

end

I wanted to be able to call ActiveMarket::Walmart.new and also ActiveMarket::Walmart::Order.new. In order to do this, I had to define class ActiveMarket::Walmart a second time as you see above and place the Order class inside. This worked as expected but I don't understand why I am able to successfully call all three of these functions.

ActiveMarket::Walmart.new.test_one
ActiveMarket::Walmart.new.test_two
ActiveMarket::Walmart::Order.new.test_all

So, the question is why does this work? Why am I able to call both test_one and test_two functions in the same class that are both defined in two completely different files? I would have expected that one of the ActiveMarket::Walmart classes to be overridden completely. Are there any downsides to this or should I change my implementation?

Thanks in advance.

Solution

Ruby allows to reopen existing classes and add additional methods to it or to override existing method.

In your example, there is actually just one ActiveMarket::Walmart class that defines two instance methods.

Try this:

walmart = ActiveMarket::Walmart.new
walmart.test_one
#=> test one
walmart.test_two
#> test two