Engines and Main App in Rails Apps
My third rails engine added to OppSites brought up some interesting challenges. The first two I installed, from Instacart’s Open Source repository, were completely self contained in their views. This third one, user_impersonate2, was my first experience with an engine that embedded itself within my own layouts.
While that behavior was necessary and useful, it was surprising when I started getting errors saying previously working path helpers were undefined.
It turns out, there is some sort of
main_app that can be appended to a
path helper to tell it to use the helper in the context of the “main app”
instead of the engine. I’m still unclear as to where
main_app is defined
and how it works exactly, but it does work.
If you were to leave off the main_app “routing proxy” method call, it could potentially go to the engine’s or application’s root, depending on where it was called from.
Ah, so it seems that
main_app forces the use application paths rather
than the paths from the current context.