Had a frustrating issue this weekend with one of my Xcode projects. I’ve been working with this project for months, without problems, and then suddenly the application won’t install onto the Simulator, and when ran onto the device, I’m greeted with the error: “The application does not have a valid signature.”

Note this is not the same as the more common invalid provisioning profile error. I of course, googled my problem with the error message, but to my surprise found very little of anyone else with the same problem.

After a slow process of elimination, I finally tracked down the problem.

In my application, the directory structure of the resource files is very important. Added folders with the default option in Xcode, adds them as a group, and in the resulting application, all the files are copied into the top directory. This creates problems with you have files which share the same name, in different directories.

The solution to this is of course use reference folders (the second option you can select when added files to the project).

This is all fine and dandy, but what caused my Xcode project to go haywire, was the fact that my reference folder was called “resources”. The solution, was simply to rename the folder to “resource” (or anything else in fact), and after a clean, it works.

Very very strange error, but thankfully with an easy fix, once you know how!