Gemfile中的Ruby版本

Question

The Ruby on Rails Tutorial by Michael Hartl uses a Gemfile without specifying a Ruby version: the ruby keyword is missing in all the applications.

When I deploy to Heroku I receive the following warning:

remote: ###### WARNING:
remote:        You have not declared a Ruby version in your Gemfile.
remote:        To set your Ruby version add this line to your Gemfile:
remote:        ruby '2.2.4'
remote:        # See https://devcenter.heroku.com/articles/ruby-versions for more information.

The tutorial says that " the costs associated with including such an explicit Ruby version number outweigh the (negligible) benefits, so you should ignore this warning for now. The main issue is that keeping your sample app and system in sync with the latest Ruby version can be a huge inconvenience ".

I am wondering whether the alternative is to keep the pace with the Ruby version at Heroku (presumably 2.2.4 at present), as the book seems to suggest, or also to specify any Ruby version it suits me. In other words, since I am using Ruby 2.2.1p85 for my application, adding ruby "2.2.1", :patchlevel => "85" would work and make Heroku adjust to this version or rather I am supposed to adjust to Heroku and add as suggested ruby '2.2.4' ?

I am using rvm and a specific gemset with a specific Ruby version, for no other reason than trying to use an environment as much close to the tutorial as possible. What is the best practice in a real context? Would you suggest to use the last Ruby version and include it in the Gemfile? Can the Gemfile leave out the Ruby version with no worries?

Answer 1

Please follow the steps to solve You can check which ruby version is associate with your app by command

heroku run "ruby -v"

It is good to have default version of ruby which is 2.2.4 in order to solve your problem. If your ruby version is older than 2.2.4 then please upgrade it.

after checking/upgrading version You can use the ruby keyword in your app's Gemfile to specify a particular version of Ruby.

source "https://rubygems.org"
ruby "2.2.4"

You will need to install and update bundler again

$ gem install bundler
$ bundle update

Answer 2

This command:

heroku run rake db:migrate

solved same problem