Rails install fails: activesupport requires Ruby version >= 2.2.2

Question

I want to create a new Rails app. I am using rvm with ruby-2.1.2. I am usint the @global gemset and plan to use bundler to manage gem dependencies. However, gem install rails fails:

$ gem install rails
Fetching: concurrent-ruby-1.0.3.pre3.gem (100%)
Successfully installed concurrent-ruby-1.0.3.pre3
Fetching: minitest-5.9.0.gem (100%)
Successfully installed minitest-5.9.0
Fetching: thread_safe-0.3.5.gem (100%)
Successfully installed thread_safe-0.3.5
Fetching: tzinfo-1.2.2.gem (100%)
Successfully installed tzinfo-1.2.2
Fetching: i18n-0.7.0.gem (100%)
Successfully installed i18n-0.7.0
Fetching: activesupport-5.0.0.gem (100%)
ERROR:  Error installing rails:
    activesupport requires Ruby version >= 2.2.2.

Yes, it is true I am using ruby-2.1.2 and not ruby-2.2.2, but shouldn't I still be allowed to use ruby-2.1.2? Are we not allowed to use ruby-2.1.2 anymore?

I thought maybe that ActiveSupport 5 was already installed in the @global gemset and that ActiveSupport 5 required 2.2.2, but actually there is no ActiveSupport 5 in the @global gemset:

$ rvm gemdir
/Users/myuser/.rvm/gems/ruby-2.1.2@global
$ cd /Users/myuser/.rvm/gems/ruby-2.1.2@global
$ cd gems
$ ls
bundler-unload-1.0.2        gem-wrappers-1.2.4      rake-10.1.0         rvm-1.11.3.9            tzinfo-1.2.2
concurrent-ruby-1.0.3.pre3  i18n-0.7.0          rdoc-4.1.0          test-unit-2.1.2.0
executable-hooks-1.3.2      minitest-5.9.0          rubygems-bundler-1.4.4      thread_safe-0.3.5

So how can I prevent this error from occurring while trying to use ruby-2.1.2?

Answer 1

You're allowed to use any ruby version of your will, however you can't use any ruby version with the latest version of Rails. When you do gem install rails you're getting the latest Rails' version (Rails 5), which isn't compatible with Ruby 2.1.2 at all.

If you really want to use Ruby 2.1.2, try this: gem install rails -v 4.2.2.

As the use of gemset, since I like this pretty organized, I never use the global. I always create a new gemset for every project. This guarantee that I can have many projects, each one with a ruby and rails version, without getting any incompatibility between the gems. This of gemset as your Ruby on Rails workspace. If you separate them by project, you will minimize the odds of oddities with gem incompatibility.

Answer 2

gem install rails

Above command will use latest version of rails, that is stable release of Rails 5, which require >= ruby 2.2.2.

We can use 2.1.2 with lower version of Rails. Please specify version at the time of installing rails may solve your issue, For Example:

gem install rails --version 4.2.4

or

gem install rails -v 4.2.4

Let me know if it works. Thank you.