When I $ load 'game.rb' in my 'irb' console it returns a stack of lines the first of which contains "Could not load SDL. (LoadError)"

Question

This is the output from $ gem env:

Michels-MacBook-Pro:~ michelfrechette$ gem env
RubyGems Environment:
  - RUBYGEMS VERSION: 2.5.1
  - RUBY VERSION: 2.2.3 (2015-08-18 patchlevel 173) [x86_64-darwin15]
  - INSTALLATION DIRECTORY: /usr/local/lib/ruby/gems/2.2.0
  - USER INSTALLATION DIRECTORY: /Users/michelfrechette/.gem/ruby/2.2.0
  - RUBY EXECUTABLE: /usr/local/opt/ruby/bin/ruby
  - EXECUTABLE DIRECTORY: /usr/local/bin
  - SPEC CACHE DIRECTORY: /Users/michelfrechette/.gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /usr/local/Cellar/ruby/2.2.3/etc
  - RUBYGEMS PLATFORMS:
  - ruby
    - x86_64-darwin-15
  - GEM PATHS:
     - /usr/local/lib/ruby/gems/2.2.0
     - /Users/michelfrechette/.gem/ruby/2.2.0
     - /usr/local/Cellar/ruby/2.2.3/lib/ruby/gems/2.2.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /Library/Frameworks/Python.framework/Versions/3.5/bin
     - /usr/local/bin
     - /Users/michelfrechette/.rbenv/shims
     - /Users/michelfrechette/.rbenv/bin
     - /usr/local/bin
     - /usr/local/sbin
     - /usr/local/mysql/bin
     - /usr/bin
     - /usr/local/heroku/bin
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin
     - /Users/michelfrechette/.RVM/bin
     - /Applications/Postgres.app/Contents/Versions/9.4/bin
Michels-MacBook-Pro:~ michelfrechette$ 

I am running a script using $ ruby game.rb, which contains:

require 'rubygame'

class Game
end

I am using rbenv to manage my versions of Ruby and it is currently set to 2.3.0-dev; once upon a time I had RVM installed on my MacBook-Pro.

When I run commands like brew update or gem update all appears to be fine.

I've tried using ruby 2.2.0, but it doesn't make a difference.

When I run ruby -v I get 2.3.0p173.

Is this occurring because I once used RVM as my version manager.

Is this the output I should be seeing when I run my file?

Last login: Tue Jan 26 16:27:35 on ttys005
Michels-MacBook-Pro:~ michelfrechette$ ruby game.rb
/usr/local/lib/ruby/gems/2.2.0/gems/nice-ffi-0.4/lib/nice-ffi/library.rb:98:in `load_library': Could not load SDL. (LoadError)
from /usr/local/lib/ruby/gems/2.2.0/gems/ruby-sdl-ffi-0.4/lib/ruby-sdl-ffi/sdl.rb:51:in `<module:SDL>'
from /usr/local/lib/ruby/gems/2.2.0/gems/ruby-sdl-ffi-0.4/lib/ruby-sdl-ffi/sdl.rb:34:in `<top (required)>'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:67:in `require'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:67:in `require'
from /usr/local/lib/ruby/gems/2.2.0/gems/rubygame-2.6.4/lib/rubygame/main.rb:22:in `<top (required)>'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:119:in `require'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:119:in `require'
from /usr/local/lib/ruby/gems/2.2.0/gems/rubygame-2.6.4/lib/rubygame.rb:44:in `block in <top (required)>'
from /usr/local/lib/ruby/gems/2.2.0/gems/rubygame-2.6.4/lib/rubygame.rb:43:in `each'
from /usr/local/lib/ruby/gems/2.2.0/gems/rubygame-2.6.4/lib/rubygame.rb:43:in `<top (required)>'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:126:in `require'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:126:in `rescue in require'
from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:39:in `require'
from game.rb:2:in `<main>'
  Michels-MacBook-Pro:~ michelfrechette$

How can I fix this?

Answer 1

I think you have to learn how to use rbenv: Choosing the Ruby Version

Choosing the Ruby Version

When you execute a shim, rbenv determines which Ruby version to use by reading it from the following sources, in this order:

1. The RBENV_VERSION environment variable, if specified. You can use the rbenv shell command to set this environment variable in your current shell session.

2. The first .ruby-version file found by searching the directory of the script you are executing and each of its parent directories until reaching the root of your filesystem.

3. The first .ruby-version file found by searching the current working directory and each of its parent directories until reaching the root of your filesystem. You can modify the .ruby-version file in the current working directory with the rbenv local command.

4. The global ~/.rbenv/version file. You can modify this file using the rbenv global command. If the global version file is not present, rbenv assumes you want to use the "system" Ruby—i.e. whatever version would be run if rbenv weren't in your path.

You can use the rbenv command to display the options and to query the status of your current environment. Check it out, it is self explaining I'd say.

Answer 2

Take a look at your PATH as displayed by gem env:

 - /Library/Frameworks/Python.framework/Versions/3.5/bin
 - /usr/local/bin
 - /Users/michelfrechette/.rbenv/shims
 - /Users/michelfrechette/.rbenv/bin
 - /usr/local/bin
 - /usr/local/sbin
 - /usr/local/mysql/bin
 - /usr/bin
 - /usr/local/heroku/bin
 - /usr/local/bin
 - /usr/bin
 - /bin
 - /usr/sbin
 - /sbin
 - /Users/michelfrechette/.rvm/bin
 - /Applications/Postgres.app/Contents/Versions/9.4/bin

You have multiple issues:

• Multiple definitions for /usr/bin and /usr/local/bin

• You have a /usr/local/bin before .rbenv/shims or .rbenv/bin

  This will cause ruby, or any command associated with Ruby, to be searched for in /usr/local/bin before any Ruby managed by rbenv. And, if it's found that will be executed, even if you want rbenv to use a different version.

• You have a remaining .rvm/bin in your home directory that could be searched if a hit didn't occur in any previous directory, possibly resulting in crashing code since nothing else it points to appears to exist any more.

To fix this:

• Look in your ~/.bashrc and ~/.bash_profile files and figure out where your PATH is being modified and clean it up. There are lots of resources on the internet explaining how PATH should be defined, but in short you want to search in your .rbenv directory before /usr/local/bin and in /usr/local/bin before any /usr/bin.
• Look in ~/.bashrc and ~/.bash_profile and make sure that rbenv is being initialized correctly. The documentation explains how to do that.
• Delete the ~/.rvm directory. rbenv and RVM do not make good companions since they're designed to do the same thing only they do it different ways. The ensuing tug-of-war if they both try to manage your Rubies will make you insane.

Programmers have to understand their underlying OS enough to not get it messed up. You need to understand how your shell uses ~/.bashrc and ~/.bash_profile, how it searches PATH and resolves the names of executables, and how rbenv is supposed to be initialized.

There are multiple answers on SO about rbenv initialization so search. You'll find the information.

Answer 3

In your question you have:

require 'rubygems'
require 'rubygame'

I don't think you will need the first require, but your problem is that you are requiring the file you're in. Try removing them altogether and running your program i.e.

# No require statements
class Game
end

Your error message says the problem is from line 2, and that is require 'rubygame'.