From: Joel VanderWerf <vjoel@...>
Date: 2008-04-16T01:07:23+09:00
Subject: Re: How to reliably setup require path

Eric Hodel wrote:
> On Apr 14, 2008, at 16:16 PM, Joel VanderWerf wrote:
>> Christian Johansen wrote:
>>> I'm writing my first Ruby command line application (beyond a simple
>>> script) and I'm little unsure about how to structure the application and
>>> the best use of require. I've come as far as to have the following file
>>> structure:
>>> myapp/
>>>  bin/
>>>    myapp
>>>  docs/ (RDOC files)
>>>  lib/
>>>    myapp.rb
>>>    myapp/
>>>      files and folders here
>>>  test/ (Test::Unit tests)
>>> And the application is working, but there are a few things of which I am
>>> unsure:
>>> The bin/myapp file is a symlink to the lib/myapp.rb file which has a
>>> shebang line. This doesn't really work, because inside lib/myapp.rb I
>>> have:
>>> require 'myapp/file'
>>> require 'myapp/module/file'
>>> which doesn't make sense when running the application from anywhere else
>>> than myapp/lib
>>> I also tried
>>> $MYAPP_ROOT = File.expand_path(File.join(File.dirname(__FILE__),
>>> 'myapp'))
>>> $LOAD_PATH << File.expand_path($MYAPP_ROOT)
>>> Which still doesn't work because this also relies on cwd...
>>> How do I work around this? What's the best practice way of making these
>>> things make sense? Do you use the $RUBYLIB variable to set the full path
>>> to the application? I was hoping to create the application as standalone
>>> as possible, so installation will be easy.
>>
>>
>> I'd do a couple of things differently (and I've used this pattern in a 
>> number of applications with the same dir structure as yours):
>>
>> 1. make bin/myapp a very short ruby script instead of a symlink (if 
>> you want this to work on windows, symlinks won't work anyway).
>>
>> 2. use unshift instead of <<, so you get precedence
>>
>> 3. use an ENV var instead of a global so child scripts can use it
>>
>> 4. use File.dirname to go up two levels instead of one, so that you 
>> can use it to find non-lib files as well (images for example, or other 
>> data files). Note that the expand_path call has to happen before 
>> calling dirname twice.
>>
>> Here's the code:
>>
>> ENV['MYAPP_BASE'] = 
>> File.dirname(File.dirname(File.expand_path(__FILE__)))
>> libdir = File.join(ENV['MYAPP_BASE'], "lib")
>> $LOAD_PATH.unshift libdir
>> ENV['RUBYLIB'] = libdir + ":" + ENV['RUBYLIB']
> 
> The simplest way is `ruby -Ilib bin/myapp` from the root of the project 
> dir.
> 
> (-I directories take precedence over RUBYLIB directories.)

It depends. The -I solution won't help with:

- making your app double-clickable (or hash-bang executable from the 
command line)

- locating other resources, like myapp/icons.

- stting up the same access (to lib and other resources) for ruby 
processes fired off by system, popen, etc.

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407