Implementing your DSL

One of the best aspects of Ruby is how easy Ruby makes it to implement a DSL. After programmer friendliness, probably the main reason you see so many DSLs in Ruby is the simplicity of implementation. There are a few different DSL types you learned about in the previous sections, and you'll learn how to implement each in this section.

The first type is the most basic type, where the DSL method accepts a block that is yielded as an object, and you call methods on the yielded object. For example, the RSpec configuration example could be implemented as follows:

def RSpec.configure
  yield RSpec::Core::Configuration.new
end

In this case, the configuration is global and always affects the RSpec constant, so the RSpec::Configuration instance may not even need a reference to the receiver.

For the Foo.process_bars example given previously, assuming the ProcessBarCommand uses the add_bar method and the DSL uses the simpler bar method, you need...