Running a ruby on rails app locally - Different versions of ruby

Question

I'm using RVM to manage the different ruby versions I have. One particular application is using an older ruby version (2.3.1), and I've noticed that, once I've changed to that version and run rails server on it, it doesn't work because I'm required to change a whole cascade of Gems or other files, such as nokogiri, to make it run.

Generally, from what I've read online, I should just do a simple bundle install to do all of this before running rails server . However, it doesn't work as there are more conflicting things in this file, specifically that the versions are hard coded into it.

Based on this, how can I run this app on my local server, if the above steps I've done, just doesn't work? I'm using Ubuntu, if that helps.

Answer 1

You're dealing with what is known as dependency issues. The point of Gemfile and Gemfile.lock is to insure that there will be no dependency issues for the application and bundle install will handle that. However it is common for versions to be set in the Gemfile to lock to a specific major release version which might allow for minor version updates. This will look something like:

#Gemfile
gem 'rails', '4.2.10'
gem 'pg', '0.20.0'

gem 'after_party', '~> 1.10' #minor version updates will run here
gem 'kaminari', '~> 1.1'

ruby '2.3.6'

This ia a brief example. Now when you run bundle install it will make sure everything is compatible with these versions. While running bundle update will only update the versions with ~> before the version and will upgrade only minor semantic versions as they are not supposed to have breaking changes.

So, why is your app not working? Well the Gemfile should have contained a ruby version. RVM should determine your ruby version in .ruby-version file in base of your rails app and should match the version in Gemfile. If you need to upgrade your ruby version bundler will help insure all your gems are compatible with that version and with each-other. You'll first need to upgrade your ruby version with RVM, then set it in Gemfile.

However, there is no guarantee that out of date gems will be compatible. That's the whole point of locking them so that you know which versions are stable at a give point in time. Updates / upgrades to gems have to be tested for compatibility which can sometimes be a project.

Also see Rails Bundle, gems conflicts, best way to solve it

Answer 2

You can create a .rvmrc file or .ruby-version and .ruby-gemset files for isolating gems for your projects. Here's the official documentation on that - https://rvm.io/workflow/projects#project-file-ruby-version

Answer 3

you can add echo '2.3.1' > .ruby-version and echo 'newgemset' > .ruby-gemset into working folder then run

cd ./
rvm install ruby-2.3.1
gem install bundle
bundle install