Simple macro like functionality for RubyMotion

app_delegate.rb

class AppDelegate
  def application(application, didFinishLaunchingWithOptions:launchOptions)
    #MBEGIN
    #if ENV['test']
    #  @contents << "self.test"
    #end
    #MEND

    true
  end

  #MBEGIN
  #if ENV['test']
  #@contents << "def test"
  #@contents << "  puts 'test'"
  #@contents << "end"
  #end
  #MEND
end

preprocessor.rb

# put in the 'lib' folder

class ProcessedFile
  def initialize(path)
    @path = path
    @contents = []
    @current_macro_lines = []
    process
  end

  def changed?
    @changed
  end

  def process
    File.open(@path) do |io|
      io.each do |line|
        if line =~ /#MBEGIN/ .. line =~ /#MEND/
          @changed = true
          @current_macro_lines << line.gsub(/\s*#/, '') unless line =~ /#MBEGIN/ || line =~ /#MEND/
        else
          eval(@current_macro_lines.join("\n"))
          @current_macro_lines = []
          @contents << line
        end
      end
    end
  end

  def contents
    @contents.join("\n")
  end
end

class Preprocessor
  def self.process(app)
    app.files.each do |file|
      pf = ProcessedFile.new(file)

      if pf.changed?
        app.files -= [file]

        system 'mkdir', '-p', File.join(File.dirname(app.project_dir), "tmp")

        tmpfile = File.join(File.dirname(app.project_dir), "tmp/#{File.basename(file)}")
        if File.exists? tmpfile
          File.delete(tmpfile)
        end

        io = File.new(tmpfile, 'w')
        io.puts pf.contents
        io.close

        app.files += [tmpfile]
      end
    end
  end
end

Rakefile

# -*- coding: utf-8 -*-
$:.unshift("/Library/RubyMotion/lib")
require 'motion/project/template/ios'
require './lib/preprocessor'

begin
  require 'bundler'
  Bundler.require
rescue LoadError
end

Motion::Project::App.setup do |app|
  # Use `rake config' to see complete project settings.
  app.name = 'Macros'

  Preprocessor.process(app)
end

Rocket science stuff! Cool.