Question

I am exploring the world of Ruby and RVM. I am going through a lot of documentation and trying out RVM, but I am a bit confused about the entire work flow. I am writing down the workflow as I understand it. Can someone please take a look and see if this understanding is correct?

I am using a Mac.

• RVM is essentially a script that allows us to manage Ruby environments for development purposes.
• RVM allows switching between different versions of Ruby with rvm use 1.9.2.
• To use a particular gemset with the current Ruby version, we need to create a gemset using
  rvm --create gemset rails235
• Install the gem using gem install rails -v=2.3.5

Q: What happens if I did gem install rails -v=2.3.5 prior to creating a gemset? Will there be two copies of the same Rails installed under RVM’s Ruby 1.9.2?

Q: What happens if I install 2.3.5 and 3.1.0 prior to creating gemsets and then create a gemset for each version?

Q: where does rvmrc come into picture in the whole story?

Any other information that helps me get this straight is extremely helpful.

Answer 1

@Kiran, this is in reference to your comment above. When you install a different version of ruby with rvm, it’ll add to this list:

$ rvm list

rvm rubies

=> ruby-1.9.2-p290 [ i386 ]

On my system, I’ve only got one version running (for now). This helps too

$ rvm gemset list

gemsets for ruby-1.9.2-p290 (found in /Users/mike/.rvm/gems/ruby-1.9.2-p290)
   global
=> mg_diaspora
   rails3
   railscasts
   ruby
   sorcery

The practice is to install common gems into your global gemset and create/use sets for everything else. I tend to keep pry and others in the global gemset. As Mike K. said, you’d never do #2; if you did do such a thing, I would imagine global having priority.

#3 .rvmrc

You can do things like this in the file:

rvm use 1.9.2@rails3 --create

This will ensure whenever you ‘cd’ into the directory, it’ll switch to 1.9.2 and it’s ‘rails3’ gemset; the following attribute ensures the gemset will be created if it doesn’t already exist.

Update

Ex: if I say rvm use 1.9.2@rails3 –create how does this pick the version of rails3.1.0 gem
Because by the time this rails3 gemset is created I already have 2 versions of rails gems?

That’s easy – when you run bundle install it creates a Gemfile.lock; this essentially ‘locks’ the gems that your application is set to use. You’ve never require two different versions of rails in a single Gemfile anyways – that’s just ridiculous =)