如何在Cloud9 IDE中正常运行基于Ruby2D gem的Ruby图形应用？

Hey there! Let’s figure out why you’re seeing that confusing "Ruby on Rails: Welcome Aboard" page instead of your red square when running Ruby2D code on Cloud9. Here’s what’s going on and how to fix it:

Why This Happens #

Cloud9 is a browser-based IDE running on a remote server—unlike your local machine, it doesn’t have a native desktop environment to render Ruby2D’s default GUI windows. Plus, Cloud9’s preview system sometimes falls back to its default Rails welcome page if it can’t find the expected content on the port your script is using.

Step-by-Step Fix #

The solution is to tell Ruby2D to run in web mode, which spins up a lightweight web server instead of trying to open a desktop window. Here’s how to adjust your code:

1. Modify your script to enable web mode and use Cloud9’s assigned port:

   require 'ruby2d'
   # Enable web mode and use Cloud9's environment port (or fall back to 8080)
   set width: 300, height: 200, mode: :web, port: ENV['PORT'] || 8080
   s = Square.new
   s.color = 'red'
   show
   

2. Run the script again in your Cloud9 terminal. You’ll still see a message like "Your code is running at..." followed by a link.

3. Click that link this time—you should see your red square rendered in the browser, no Rails welcome page in sight!

Extra Tips to Avoid Conflicts #

• Use a dedicated folder: Keep your Ruby2D projects separate from any Rails projects in your Cloud9 workspace. This prevents environment mix-ups that might trigger the Rails welcome page.
• Check port usage: If you still run into issues, make sure no other processes are using the port your script is assigned to (you can use lsof -i :PORT_NUMBER in the terminal to check).

内容的提问来源于stack exchange，提问作者Waterman33