Why do I get "Could not find mail-2.2.9.1 in any of the sources" after updated Ruby and Rails?

I recently updated my Ruby version to 1.9.2 through RVM. (And, is it normal that I have to use the command rvm use 1.9.2 EVERY TIME when sta开发者_Python百科rting the terminal?).

I deleted some Rails files I shouldn't have, so I reinstalled Rails. However, I still get this error when trying to generate controllers:

Could not find mail-2.2.9.1 in any of the sources

Try running bundle install.

Running bundle install solves the problem for the moment, but I get the same error when starting another project.

you need to use an rvmrc file. it tells rvm which ruby version / gemset to use. read:

https://rvm.io/workflow/rvmrc/