Global variables in Rails

A quick note, because I was using the wrong search terms. If you want to share e.g. the current user of an app with a model you can now (since Rails 5.2) use a model inheriting from ActiveSupport::CurrentAttributes. Before you were required to pass this current user explicitly or find another way to access state.

Note that this can either be a good thing or a bad thing (tl;dr: thread-local global state makes apps unpredictable)

And even the docs warn against abusing this feature. Powerful tools can come with dangerous consequences :) Global variables are immensely powerful. Use with care. I'm not even sure if I'm going down this path…