A DSL implementation based on Bundler

Here is an implementation of a real basic DSL. The implementation was lifted from bundler.

Summary

The main idea is you have a class Dsl that you call instance_eval on. Your domain specific language is still written in ruby, but by evaluating it within the context of an instance of Dsl, you can create the illusion of top level language constructs. These are merely public instance methods of Dsl. This is the way bundler evaluates a Gemfile.

Example

Here is an example, using the implementation in the gist below.

  dsl = Remote::Dsl.new
  dsl.server :app1, "admin@192.168.1.1"
  dsl.server :app2, "admin@192.168.1.2"

By using instance_eval we can turn the above into

  server :app1, "admin@192.168.1.1"
  server :app2, "admin@192.168.1.2"

Examples of this type of DSL:

• Gemfile
• Capfile
• Rakefile
• config/routes.rb in Rails

Implementation