The first step is to convert our Objective-C Cocoa application into a RubyCocoa application. Our application will need to have a Ruby interpreter and the RubyCocoa bridge code built into it. To get them, make the following changes:

• Add the RubyCocoa framework to your project.
  • In the ‘Groups & Files’ section on the left side of the Project window, expand the ‘Frameworks’ group,
  • Right-click (or Ctrl-click) on the ‘Linked Frameworks’ group, and choose ‘Add -> Existing Frameworks…’
  • Find and add ’/System/Frameworks/RubyCocoa.framework’

• Replace main.m with the following code:

#import <RubyCocoa/RBRuntime.h>

int main(int argc, const char *argv[])
{
    return RBApplicationMain("rb_main.rb", argc, argv);
}

• Add a new file to your project named rb_main.rb. Give it the following contents:

require 'osx/cocoa'

def rb_main_init
  path = OSX::NSBundle.mainBundle.resourcePath.fileSystemRepresentation
  rbfiles = Dir.entries(path).select {|x| /\.rb\z/ =~ x}
  rbfiles -= [ File.basename(__FILE__) ]
  rbfiles.each do |path|
    require( File.basename(path) )
  end
end

if $0 == __FILE__ then
  rb_main_init
  OSX.NSApplicationMain(0, nil)
end

Now build and test your application. Everything should work just as before, but your application now has a hidden and very special power—it can run Ruby code. We’ll use this in the next three chapters to convert the three classes Controller, CustomWindow, and CustomView one-by-one into Ruby, and then in the next chapter to make some fun and easy enhancements. We’ll convert the classes one at a time so that we can catch any problems that appear along the way.