Require - No Such File to Load Ruby

The exercise I'm working through in Learn Ruby the Hard Way has me spending a week creating my own game. I've been building various text-based adventure games, but was stuck on what to do next. This morning on the way to work I got the idea of building a MadLib generator.

The way I picture it working is like this: the generator will ask the user to select a Mad Lib from a list, then ask for the requisite input (nouns, adjectives, verbs) depending on the Mad Lib selected and finally spit out the finished product. Simple, right?

So my thinking is this project would be split into two parts: the main program that asks for which Mad Lib the user wants to do, and the Mad Lib that is loaded upon selection. To get this up and running, I decided just to make one Mad Lib work at first, then add support for multiple Mad Libs and the ability to choose between them.

This is just a simple matter of requiring the Mad Lib file from the Main file, but I ran into a small problem.

Using the require 'mermaid' command threw this error:

<internal:lib/rubygems/custom_require&rt;:29:in `require': no such file to load -- mermaid (LoadError)

I wasn't sure why this wasn't working, since I've used require to load separate .rb files before. After a bit of digging around, all I had to to do fix this problem is change require 'mermaid' to require_relative 'mermaid'. This makes sense - both files are in the same directory, so this command is simply saying to require this file located in the same directory as the main file.

On a side note, I'm glad to have fixed the problem, but I'm getting to the point that I think it's better to understand WHY things don't work, rather than finding the solution and moving on. Can anyone tell me why 'require' wasn't working, but 'require_relative' does? Is it an older style of Ruby code that's outdated? Do I need to change some configurations? Is require_relative a workaround? Where does require look for files, if not in the same directory the file that's making that call is located?

Anyway, it felt good to make some progress on this tonight. It's pretty awesome that I can come up with an idea on the way to work, come home and put it together in an hour and a half or so. I think this will be a fun little project. I plan to work on it more this weekend, expanding it, polishing it up and so on. Here's a link to the gist I made of it:

MadLib Generator