Notes on Rebuilding Rails

Currently reading Rebuilding Rails by Noah Gibbs.

Notes:

Chapter 3

Sometimes, Noah writes methods in the context of a module, sometimes in the context of a class. Why?

Modules are collections of methods and constants. They cannot generate instances. Classes may generate instances (objects), and have per-instance state (instance variables). Source

Checking rails/active_support_dependencies/autoload.rb and I see this @_at_path. What is the reason for this @_?

So, @_instance_var has no special meaning. Rails internally uses it to distinguish private/protected variables that other should not modify/access. source

bundler: failed to load command: rackup Couldn't find handler for: puma, thin, falcon, webrick. (LoadError)

If you run into bundle exec rackup -p 3001 bundler: failed to load command: rackup. Couldn't find handler for: puma, thin, falcon, webrick. (LoadError), look closely at your gemspec, and at the configuration described by Noah page 18.