使用Cloud9开发自定义Gem部署至Heroku时遇“Custom gem is not a class”错误

Hey there, let’s break down why this might be happening and how to troubleshoot it step by step!

1. Gem Load Order or Require Mismatch #

Heroku’s production environment handles gem loading differently than your local Cloud9 setup. Double-check these details:

• Ensure your Gemfile correctly references your custom gem (if it’s hosted in a Git repo, use the git: option instead of a local path, since Heroku can’t access your Cloud9 filesystem). For example:

  gem 'your_custom_gem', git: 'https://your-git-repo-url.git'
  

• Verify the require statement in your app matches your gem’s file structure. If your main class lives in lib/your_custom_gem.rb, your app should use require 'your_custom_gem'—not a nested path unless you’ve intentionally structured it that way.
• Check your gem’s gemspec to confirm require_paths includes lib (this is default, but accidental modifications can break loading).

2. Case-Sensitive Naming or Typos #

Ruby is case-sensitive, and small typos can cause this error even if everything works locally:

• Make sure the class name in your gem (e.g., YourCustomGem) exactly matches how you’re referencing it in your app (no mixing your_custom_gem lowercase when you mean the camel-case class).
• Rule out naming conflicts—ensure no other gem or local application class shares the same name as your custom gem’s class on Heroku.

3. Heroku Gem Installation Issues #

Sometimes Heroku fails to properly install the gem, which prevents the class from being available:

• Run heroku run bundle show your_custom_gem to confirm the gem is installed on your Heroku dyno.
• Check your deployment logs with heroku logs --tail—look for errors during gem installation (like missing dependencies or repo access issues) that might be silent during local testing.

4. Autoloading Discrepancies (for Rails Apps) #

If this is a Rails app, Heroku’s production environment disables automatic class loading by default. You might need to:

• Add an explicit require for your gem’s class in an initializer (e.g., config/initializers/load_custom_gem.rb with require 'your_custom_gem').
• Avoid relying on Rails to autoload the gem’s class in production—explicit requires are safer here.

5. Gem Structure Problems #

Ensure your custom gem follows Ruby gem conventions:

• Your main class should be defined in a file that matches the gem name (e.g., lib/your_custom_gem.rb for gem named your_custom_gem).
• If your class is nested inside a module, make sure you’re referencing it with the full namespace (e.g., MyModule::YourCustomGem instead of just YourCustomGem).

内容的提问来源于stack exchange，提问作者M. Hayden