I'm using the RMagick gem. If you require 'RMagick', it will give you an error, saying to use require 'rmagick', lowercase, instead. If I follow its advice, Ruby and Rubinius work fine, but JRuby throws a no such file to load -- rmagick exception.
It looks like Ruby has changed whether it wants lowercase gem names, but JRuby hasn't? What's the problem here and what would the proper solution be?
you're probably using two different require "paths" (gems) ... since RMagick is C-ext based it works under MRI+Rubinius. under JRuby if you'd had the very same RMagick gem trying to load it would sure fail. take a look at what gets actually loaded under JRuby.
Related
My gem uses rubyinline for some ruby-evil style stuff (I don't like it but it's the only way to do what I want) and uses rubyinline to do it.
So I've added it to my .gemspec with:
spec.add_runtime_dependency "RubyInline"
but when I try to test the gem, ruby keeps reporting:
'require': cannot load such file -- inline (LoadError)
But when I add to the test's Gemfile:
gem 'RubyInline'
It suddenly starts working (well, ok, it errors but for an entirely unrelated reason).
I can see that the correct version of rubyinline is installed as well, so I know it's not that.
whats going on? Why won't it accept that rubyinline is there unless I add it to the gemfile?
I'm new to Ruby and I'm having a lot of trouble trying to use Nokogiri. I've been trying to find a resolution for hours now, so any help is appreciated. I tried searching for and using solutions from other related SO posts before caving and posting my own. When I run ruby -v I get: ruby 1.8.7 (2011-06-30 patchlevel 352) [x86_64-linux]
(Edit: I have updated ruby with updates-alternatives --config ruby and selected /usr/bin/ruby1.9.1 but when I do ruby -v it is now showing version 1.9.3 WTF am I doing wrong here?)
I have a new project directory at ~/workspace/ruby/rubycrawler/ and I used Bundler to install nokogiri, which installed correctly:
Using mini_portile (0.5.2)
Using nokogiri (1.6.1)
Using bundler (1.5.1)
Your bundle is complete!
Running bundle show nokogiri returns /var/lib/gems/1.9.1/gems/nokogiri-1.6.1.
In the directory I'm running the script from I have a simple html file named "index.html". The script I'm trying to run is even simpler (or so I thought):
require 'nokogiri'
page = Nokogiri::HTML(open("index.html"))
puts page.class # Nokogiri::HTML::Document
The error is rubycrawler.rb:1:in 'require': no such file to load -- nokogiri (LoadError).
I also added require 'rubygems' even though I read it isn't needed for 1.9+ and still no luck.
A lot of searching shows "Did you put this gem in your Gemfile?". So I generate a Gemfile and add gem 'nokogiri'. I try running the small script again and get the same error. I read "Try deleting Gemfile.lock." so I did but still couldn't get it to work. I then read to try testing it out in irb so I tested "open-uri" and "nokogiri" and here's what I got:
irb(main):001:0> require 'open-uri'
=> true
irb(main):003:0> require 'nokogiri'
LoadError: no such file to load -- nokogiri
I'm really having a lot of trouble figuring this out, so really any help at all is really appreciated.
Ruby tools like RVM, Bundler, etc., to the novice, appear to do a lot of magic, but really, there is no magic to them. The key here lies in what Bundler actually does for you. It manages a manifest of dependencies, BUT at runtime, those dependencies STILL have to get loaded somehow, and my gut feeling is that is what is not happening here.
Regardless of what version of Ruby you are using, if you are using Bundler, there's an easy way to do this. Precede the command that starts your program with "bundle exec" and that will make Bundler edit Ruby's load path so that it includes all the things in the manifest (Gemfile.lock).
For example:
$ bundle exec ruby foo.rb
A additional note for anyone using RVM: RVM generally will modify the shebangs in the scripts that launch programs like "ruby" or "rake" so that they use the "ruby_no_exec" shell (or similar) instead of the plain old "ruby" shell. That alternate shell is Bundler-aware and makes it generally unnecessary to type "bundle exec," but since the OP is using system Ruby, that's not applicable and commands should be manually prefixed with "bundle exec".
Hope this helps!
In addition to Kent's answer, I would recommend switching to RVM instead of using the system installed ruby. System rubies tend to be horribly out of date, especially when it comes to important things like features and security updates. It might not help you in your current situation, but it would be well worth the time. If you are unfamiliar: http://rvm.io
I think I have a basic understanding of what require/include statements at the top of a ruby script are doing, like
require 'rspec'
These statements are easy to google and find relevant results. But sometimes I have seen a gem statement like
gem 'rspec'
What does this line do?
In ruby code, gem(gem_name, *requirements) defined in Kernel tells Ruby to load a specific version of gem_name. That's useful when you have installed more than one version of the same gem.
For example, if you have installed two versions of rspec, say 2.12.0 and 2.13.0, you can call gem before require to use specific version. Note that gem should come before the require call.
gem 'rspec', '=2.12.0'
require 'rspec'
A gem 'gem_name' without version uses the latest version on your machine, and that's unnecessary. You can call require without gem to get the same behavior.
And besides, in Bundler::Dsl, gem is used to tell bundler to prepare/install specific version of ruby gems. You'll see that in Gemfile
The original behaviour of require, before Rubygems, was to search all the directories listed in the $LOAD_FILES variable for the file, and to load the first one it finds that matches. If no matching file was found, require would raise a LoadError.
Rubygems changes this process. With Rubygems, require will search the existing $LOAD_PATH as before, but if there is no matching file found then Rubygems will search the installed gems on your machine for a match. If a gem is found that contains a matching file, that gem is activated, and then the $LOAD_PATH search is repeated. The main effect of activating a gem is that the gems lib directory is added to your load path. In this way the second search of the load path will find the file being required.
Normally this will mean that the latest version of a gem that you have installed gets activated. Sometimes you will want to use a different version of a gem, and to do that you can use the gem method. The gem method activates a gem, and you can specify the version you want, but doesn’t require any files. When you later require the files you want, you’ll get them from the gem version you specified.
In Ruby, gems are packages with functionality that can be used out of the box (as libraries in other Programming languages).
The gems that you use with your Ruby Project can easily be managed with a tool called "bundler", just google it. The snippet of code you posted is part of the spec file that bundler uses to install and update all the libraries that you specify for your project.
If you are developing a Ruby on Rails, using gems an managing them with bundler is very common and so to say best practice.
Gems are just great because there are so many useful libraries that extend default functionality, eg of rails, and that you can use out of the box!
For a list of gems, visit rubygems.org
I'm kinda new to ruby and I'd like to use a gem charting library, but for some reason when I require it in the ruby script on my desktop it doesn't work. However when I require in my irb it does work. Is there a way to fix this?
Try using bundler if you can and declare the requirements in a Gemfile. This will make your environment much more consistent between different computers and will provide a reference of the dependencies you have.
The Bundler setup procedure is pretty simple and well documented. It will load in all the gems and any of their dependencies automatically.
Generally the problem with the require statement failing is the library is not in your $LOAD_PATH, and that's usually because you haven't loaded rubygems:
require 'rubygems'
gem 'somegem'
require 'somegem'
I just wanted to understand for my self.
I'm using the nokogiri gem (for parsing HTML). If I got it right to open URLs I need to use a method from the gem 'open-uri'.
But when I include it in my Gemfile (on Windows developer's machine):
gem 'open-uri' - there is an error while bundle install that it can not find gem.
So If I use require 'open-uri' - its working.
So can some explain what is going on?
You're using bundler for your gem dependecies and you're doing it right but OpenUri is part of the Ruby standard library. That's why you only need to require it if you want to use it in your code.
require is used to load another file and execute all its statements. This serves to import all class and method definitions in the file. require also keeps track of which files have been previously required so it doesn't execute it twice.
A RubyGem is a software package, commonly called a “gem”. Gems contain a packaged Ruby application or library. The RubyGems software itself allows you to easily download, install, and manipulate gems on your system.
- What is a Gem?:
The Gemfile is then used by bundler to install the specified gems.
open-uri is not a gem but part of the Ruby Standard Library so it just needs to be required.