Before upgrading rails, it’s a good idea to upgrade other dependencies to make sure you have compatible versions of those gems.To check for newer versions of gems in your bundle, use the command.
Update the Gemfile with the newer version of Rails. so you might need to compare the diffs to make sure things like your mail configuration for production hasn’t been changed to the Rails defaults.
At this point, you’ll most probably run into a some failing tests. Also pay attention to the deprecation warnings that you might come across when running the tests.
This will list all the dependencies that have a newer version than the one in your
Go through the list and look for gems that might not be compatible with the newer Rails.
If you need assistance with Rails Installer, please see our Google Group where you can view posts from other users as well as ask questions.
Any bugs with the installer should be reported on Github in the respective repositories ( railsinstaller-windows or railsinstaller-nix ).
If you’re on Rails 3.2, it is tempting to upgrade directly to Rails 4.2. Instead, upgrade first to 4.0.x, then 4.1.x, and finally 4.2.x.
Making incremental upgrades allows you to focus on what has changed in each of those versions.
I think I have all of this going now, but when I type: Michaels-Mac Book-Pro:~ Paranoid Android$ gem install rails --version=4.0 Building native extensions. ERROR: Error installing rails: ERROR: Failed to build gem native extension. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=$/include --with-opt-lib --without-opt-lib=$/lib --with-make-prog --without-make-prog --srcdir=.
/usr/local/rvm/rubies/ruby-1.9.3-p392/bin/ruby *** failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. --curdir --ruby=/usr/local/rvm/rubies/ruby-1.9.3-p392/bin/ruby --with-atomic_reference-dir --without-atomic_reference-dir --with-atomic_reference-include --without-atomic_reference-include=$/include --with-atomic_reference-lib --without-atomic_reference-lib=$/lib /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file.
(Runtime Error) You have to install development tools first.