Why am I not able to use these lines in a Gemfile:
gem 'date'
gem 'pp'
Must these be required in file instead like this:
require 'date'
require 'pp'
Or is there a way to mix them into your Gemfile so they are available project wide?
I think that date and pp are part of ruby 1.9.2 core and as a result are different from regular gems but I don't exactly understand why...
Because those are not Gems but part of the Ruby standard library. But the standard library isnt loaded by default, hence the require statements
Related
I'm writing a batch script as a setup for a ruby program I'm writing. It needs to be able to
a. Make sure Ruby is installed on the user's computer (and if not point them to the ruby download page)
b. make sure the ruby "yaml" gem is installed, which is a prerequisite for it. I've tried
gem install yaml
in the batch script to no avail. How can I write a batch script that will do these two things?
As far as I know, there is no yaml gem. Although it must be required in code that uses it, it is distributed as part of a Ruby installation. Try this:
ruby -ryaml -e"puts 'YAML found'"
It should work; and if you change the -r token to some nonexistent gem, you'll see an exception raised.
Instead of writing your own script, you could use bundler and create a gemfile. This way people can install all the gems on any operating system.
Example:
require 'rubygems'
require 'bundler/setup'
require 'nokogiri'
require 'rest-client'
#require all your gems like normal
def parse(site)
Nokogiri::HTML(RestClient.get(site))
end
And for the gem file:
source: "https://rubygems.org"
gem 'nokogiri', '~> 1.6.7.2' #<= you can specify which version
gem 'rest-client' #<= you don't have to specify a version though
After you've got everything set up, cd to the directory that has the gemfile and run bundle install this will install all the gems
I've got a wrapper for my Gem, socks, inside socks.rb. The entire file is made up of require statements, and a module declaration:
# lib/socks.rb
require 'socks/version'
require 'socks/base_controller'
require 'socks/templates'
require 'socks/tasks'
require 'socks/rake_tasks'
module Socks
end
However, require 'socks/tasks' and socks/rake_tasks is giving me a LoadError: no such file to load -- socks/tasks / rake_tasks error.
Is this a problem with the alignment of the require statements, or just the code?
Code is on Github: https://github.com/Beakr/socks
EDIT: require './socks/tasks' is now working, however require './socks/rake_tasks' is not.
Ruby load files using its $LOAD_PATH. This global array is changed by e.g. rubygems and bundler to allow to find libraries in various locations. In your sock.gemspec you have defined
gem.require_paths = ["lib"]
which means that rubygems will add the lib directory of your gem to ruby's $LOAD_PATH. But it odes so only if you have installed the gem and the gemspec is thus evaluated. If you don't want to install your gem, you can test your gem using
bundle exec irb
in your gem directory, or alternatively by first adapting your $LOAD_PATH in your irb session like so:
$LOAD_PATH.push "/path/to/your/gem/lib"
require 'socks'
I'm trying to use rake in my ruby script...(Ruby 1.8.6, JRuby 1.6.5)
Downloaded rake using gem install --remote rake, looks ok on install...
Fetching: rake-0.9.2.2.gem (100%)
Successfully installed rake-0.9.2.2
1 gem installed
I've got a simple ruby script which works fine, but when I import rake to using any of the following requires, it starts complaining....
require 'rake'
LoadError: no such file to load -- rake
or
require '/lib/rake'
LoadError: no such file to load -- lib/rake
After some searching, I found that adding require 'rubygems' just before rakefixes the issue....
require 'rubygems'
require 'rake'
Even though it's working, I've got some questions...
The gem spec on rake shows the require_path as lib, so why
doesn't require '/lib/rake' work? Am I misunderstanding the significance of require_path?
Why is it necessary to place require 'rubygems' before require
'rake'
Yes, you are misunderstanding the significance. The require_paths in the specification is an array of subdirectories of that gem's installation directory that should be searched for files belonging to the gem.
To find out where rake really is, try this:
$ gem which rake
You'll see that it is actually installed somewhere completely unrelated to /lib; on my system, it's under /var/lib/gems. Ruby gems, in general, live in their own directory structure; the only file in the standard Ruby include path ($:) is rubygems itself, which you used to have to explicitly require in order to make any actual gems visible. (Since Ruby 1.9, that has not been necessary.)
Gems are more complex than just libraries to load; you can have multiple versions of the same gem installed, and specify which one you want at a time, and do other things that wouldn't work if the gems were just dumped into the standard Ruby include path.
The require_path in the gemspec tells ruby where the files of this gem are located within the gem. It makes you able to type require 'rake', and ruby then knows it needs to look for /lib/rake within the gem installation folder.
In Ruby 1.8, rubygems (the mechanism responsible for making gems available to your app) is not loaded by default, and the default ruby isn't aware of any gem on your system. You need to load rubygems before being able to require any other gem. This is not the case anymore with Ruby 1.9.
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 have seen many samples of Ruby code with this line (for example, http://www.sinatrarb.com/). What is purpose of this require?
# require 'rubygems'
require 'sinatra'
get '/hi' do
"Hello world!"
end
In all cases the code works without this line.
require 'rubygems' will adjust the Ruby loadpath allowing you to successfully require the gems you installed through rubygems, without getting a LoadError: no such file to load -- sinatra.
From the rubygems-1.3.6 documentation:
When RubyGems is required, Kernel#require is replaced with our own
which is capable of loading gems on demand.
When you call require 'x', this is what happens:
If the file can be loaded from the existing Ruby loadpath, it
is.
Otherwise, installed gems are searched for a file that
matches. If it's found in gem 'y', that gem is activated
(added to the loadpath).
The normal require functionality of returning false if that file
has already been loaded is preserved.
See the documentation for Kernel#require to understand why this is necessary.
It is often superfluous. It will allow you to require specific versions of particular gems though, with the gem command.
https://guides.rubygems.org/patterns/#requiring-rubygems
As an addition to prior (and correct answers): Ruby 1.9 and newer ship with RubyGems built-in, so there is no real need to require 'rubygems'. Source here