Virtuous Code - Latest Comments in Double-Load Guards in Ruby

Re: Double-Load Guards in Ruby

Mike Subelsky — Mon, 15 Feb 2010 15:02:11 -0000

I found the File.expand_path two-argument trick useful for writing some code that works both in Ruby 1.8 and 1.9 (where require behavior changes)

Re: Double-Load Guards in Ruby

Mike Subelsky — Mon, 07 Dec 2009 12:22:05 -0000

Another awesome post Avdi! We were having some hard-to-trace double constant definitions and using this code in my Rails pre-initializer TOTALLY surfaced them. Thanks!

Re: Double-Load Guards in Ruby

François Beausoleil — Fri, 23 Oct 2009 21:19:52 -0000

Why not use Ruby 1.9, which fixed the problem by storing the expanded path in the require table? http://eigenclass.org/hiki/...

Re: Double-Load Guards in Ruby

The Konstantin — Fri, 23 Oct 2009 17:55:18 -0000

You're right. But specs/tests is about the only place I do so myself.

Re: Double-Load Guards in Ruby

Avdi Grimm — Fri, 23 Oct 2009 09:55:05 -0000

Konstantin, thanks for your comment. Setting up $LOAD_PATH is essential and I make sure to add the current project to the load path in all but the smallest of projects.

However, there are always a few files where relative requires can't be avoided. For instance, it is conventional to set up unit test/spec files so that they can be run standalone. In order for this to work each test file has to start out by requiring a test_helper.rb or a spec_helper.rb which then sets up $LOAD_PATH, requires additional libraries, etc. Because this test helper is the first thing to be loaded and can't rely on anything else to be configured, it has to be loaded with a relative path.

This is where I see the most double-loads occurring, because when all of the tests are run together they each require the test helper file, often with differing relative paths. Using expand_path is a way to ensure that files that must loaded relatively are required in a consistent way.

I may update the post to make it clear that I'm not suggesting you use relative requires throughout a project.

Re: Double-Load Guards in Ruby

The Konstantin — Fri, 23 Oct 2009 04:05:12 -0000

I disagree. Doing require File.expand_path is way to ugly. Just setup you $LOAD_PATH correctly and you will not encounter any of such problems. Treat your code as if it was a library.