Rails: AbstractController::Helpers::MissingHelperError - Missing helper file application_helper.rb_helper.rb

Question

Can\'t find any resource that\'s helped me in this! When I try to \'rails s\' and go to any page of the app; it shoots me this error page saying I am missing helper files.

Answer 1

This isn't really a ruby or Rails bug as it is a flaw in OSX (IMHO) resulting from a design decision made many years ago to maintain compatibility with OS 8.0 (classic MacOS) and provide better compatability with Windows FAT/NTFS. That decision was to implement HFS+ with a case preserving but case insensitive naming schema wherein the following paths are equivalent:

 /tmp/CASE_insensitive
 /tmp/case_INSENSITIVE

You can read more about this in the following quora post:

Why does OS X choose to have a case-insensitive file system instead of a case-sensitive one?

If you've ever configured an HFS+ filesystem to enforce case insensitivity (you know, to be more compatible with actual *nix filesystems) you may very well come across software that just breaks on OSX because that software has been somewhat carelessly written to assume no case insensitivity (IIRC, some Adobe software had great trouble with HFS+ with case sensitivity).

Try this in the OSX terminal:

 prompt>mkdir /tmp/CASE_insensitive
 prompt>cd /tmp/case_INSENSITIVE
 prompt>pwd
 /tmp/case_INSENSITIVE

IMHO, that's pretty messed up. Now, if you're using Pow on your OSX system, when you create the symlink in the ~/.pow directory to point to your Rails app, be careful of the case. Mis-typing the case here will result in the error noted by the OP. Simply removing and renaming the symlink with the appropriate case will fix this properly.