Why relative path doesn't work in Ruby require

Question

I'm starting learning Ruby, one thing that I don't understand, why relative path for require directive doesn't work in ruby. It's something that works almost in every scripting language that I now (JSP, PHP...). I explain with a real example. I have a folder named shapes which contains 3 classes shape, rectangle and square. I have also another file test_shapes.rb from where I call and test my classes. When I import my classes to the main file like this:

require "./shape" require "./rectangle" require "./square" 

I got error for files not found. When I include the name of my subfolder like this:

require "./shapes/shape" require "./shapes/rectangle" require "./shapes/square" 

The code is perfectly working. Because I specified the whole path to the root directory of the project (the lib folder I think). When I include I include the absolute path to the hard disk, like this:

require "#{File.dirname(__FILE__)}/shape" require "#{File.dirname(__FILE__)}/rectangle" require "#{File.dirname(__FILE__)}/square" 

It's also working perfectly.

So, I just want some explanation if know why the first import method (the relative path to the current folder) in not working.

Answer 1

Relative path is based on working dir. I assume that there is main file on the same directory. If you run ruby ./shapes/main.rb on project root, ruby try to find {project_root}/shape.rb, not {project_root}/shapes/shape.rb. It doesn't work.

You need to use require_relative like below.

# {project_root}/shapes/main.rb require_relative './shape' require_relative './rectangle' require_relative './square' 

Answer 2

You are using relative path. And they are relative to the place where your script is executed. Generally it is bad idea. You should use either absolute path, either relative path to exact file where require is executed.

require File.expand_path("../shape", __FILE__) 

PS: require_relative looks more laconic