Ever want to pop into the source code of some gem that you are using?

Gem Edit is a nice and easy way to do this (if you aren’t using RubyMine, for example):

[sudo] gem install gemedit

In the terminal, simply type:

[develop*]$  jonsmac2-2:source jon$  gem edit -e mate mongo_mapper

And you will see:

Found gem for 'mongo_mapper' with version >= 0
Opening the following gems with mate:
  mongo_mapper-0.8.6 /Library/Ruby/Gems/1.8/gems/mongo_mapper-0.8.6
Running `mate "/Library/Ruby/Gems/1.8/gems/mongo_mapper-0.8.6"`

and Voila, Mongo Mapper appears in TextMate:

Mongo Mapper Source Code

In an IDE, you can often get to the source code for a single method, but not as “completely” as with gemedit and TextMate, IMHO.

Mongo Mapper from IDE

@martinstreicher gave me a good tip when using bundler (which I use on my Rails 3 apps):

export EDITOR=mate;bundle open <gem>