DSL Example

dsl.rb

#! /usr/bin/env ruby

module SomeMod

  module DSL

    def self.included(base)
      base.extend ClassMethods
    end

    module ClassMethods

      def some_dsl(**opts, &block)
        Context.new(self, **opts, &block)
      end

    end

    def some_dsl(**opts, &block)
      Context.new(self, **opts, &block)
    end

  end

  class Context

    attr_reader :target, :options

    def initialize(target, **opts, &block)
      @target = target
      @options = opts
      instance_exec &block
    end

  end

  class Action

    attr_reader :context, :run_block

    def initialize(context, &block)
      @context = context
      @run_block = block
    end

    def call
      run_block!
    end

    private

      def target ; context.target ; end

      def run_block!
        instance_exec &run_block if run_block.is_a?(Proc)
      end

  end

  def register_action(name, klass)
    raise 'Can only register a descendant of Action' unless klass < Action
    Context.send(:define_method, name) do |*args, &block|
      action = klass.new(self, &block)
      action.send(:call, *args)
      action
    end
  end
  module_function :register_action

end

class LogAction < SomeMod::Action
  def call(msg)
    puts '='*50
    puts "context: #{context.inspect}"
    puts "message: #{msg}"
    puts '='*50
  end
end
SomeMod.register_action :log, LogAction

class SomeBlockAction < SomeMod::Action
  def foo
    puts "foo"
  end
end
SomeMod.register_action :some_block, SomeBlockAction

class SubDSLAction < SomeMod::Action
  include SomeMod::DSL
  def call
    some_dsl &run_block
  end
end
SomeMod.register_action :sub_dsl, SubDSLAction

class MyClass
  include SomeMod::DSL

  foo = 'test'
  some_dsl do
    log foo
  end

  def do_dsl_stuff(bar)
    some_dsl a: 1, b: 2 do
      log bar
      main_context_options = options
      sub_dsl do
        log main_context_options.inspect
        sub_dsl do
          log 'nested 1'
          sub_dsl do
            some_block do
              foo
            end
          end
        end
      end
    end
  end

end

MyClass.new.do_dsl_stuff('FOO')