Seeing is Believing

Since embarking on my programming journey, I have to admit - I have gone a little gem-crazy. It’s just so EASY to type gem install the_promise_of_magic. I think that’s one of the more dangerous aspects of living in the command line. When I’m considering installing something via the browser, there are a multitude of clues to help you ascertain whether or not a binary is legit, not least how polished their site looks.

There is also a kind of false sense of security that can set in when you’ve been a Mac user for your entire adult life, and have not traditionally had much cause to worry about virus issues etc, so to just type three words into your iTerm and wait for your latest library to make itself comfortable in your filesystem takes little effort. This is something I have noticed and am now very mindful of - but I digress…

This post is really to draw your attention to a frankly wonderful wee gem I found this week, called ‘Seeing Is Believing’, developed by Mr Josh Cheek. Based on an existing gem called rcodetools, it automagically places a comment at the end of each line of ruby code containing the evaluation. Pretty friggin’ useful for a beginner. You can see a video of this little beaut being demonstrated here.

So how could this be even better Roi? How about Sublime Text integration? Ding Dong! (Josh also supports Textmate 1-2 and Vim)

There is one wee-tiny-little catch - if you’re new at this stuff, the documentation is a little bit sparse (I found the whole rvm wrapper thing a bit mysterious to say the least), so I thought I would do a quick write-up. Now bear in mind that I work with a ruby version of 2.1.1 on a mac using rvm Ruby Version Manager so I can only tell you what worked for me, and this is it.

First one must install the gem:

gem install seeing_is_believing

Then you need to navigate to the following folder:

cd ~/Library/Application\ Support/Sublime\ Text\ 2/Packages

and inside of that directory, clone this repo:

git clone git://

If this is confusing for you, I would recommend researching into how to navigate your file system using the command line and basic usage of Git. Next up, you need to make a wrapper for Sublime (this is the bit that I found confusing), and for this you need to know which version of ruby you are currently running. On my setup, I can type ruby -v and am rewarded with the output:

ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin12.0]

I take the section ruby 2.1.1 and type the following into Terminal:

rvm wrapper ruby-2.1.1 sublime

Now, at this point you need to run the following command in terminal : which sublime_ruby, which will return a line like this: /Users/your-username/.rvm/bin/sublime_ruby At this point, you need to open ‘SeeingIsBelieving/Seeing Is Believing.sublime-settings’ in Sublime Text and comment out the line "RBENV_VERSION": "2.0.0-p0" and the MOST important part: delete "ruby_command": "~/.rbenv/shims/ruby", and replace with the following:

"ruby_command": "~/.rvm/bin/sublime_ruby",

where the line "~/.rvm/bin/sublime_ruby", matches the line you got when you typed in which sublime_ruby - remember that? ;)

Restart Sublime Text, and enter some ruby code:

10.times do |i|
  i * 2

Now if you hit the pre-defined keyboard shortcut (⌥ + ⌘ + B on OS X) or run the command:

Evaluate Ruby code with Seeing Is Believing

from your command pallete (⌘ + ⇧ + P), you should see the following output:

10.times do |i|
  i * 2          # => 0, 2, 4, 6, 8, 10, 12, 14, 16, 18
end              # => 10

To remove the comments, run Remove Seeing Is Believing annotations or press (⌥

Well there you have it - instant win! I strongly suggest that you take the time to watch Josh’s video (and browse the documention I linked to earlier) - I have directly referenced a lot of the material for this article and I cannot recommend this enough as a tool to get your head around what ruby is doing when it evaluates your code.

Happy coding! ^_^