gem interview questions
Top gem frequently asked interview questions
I have several versions of a Ruby gem:
$ gem list
rjb (1.3.4, 1.3.3, 1.1.9)
How can I remove old versions but keep the most recent?
Source: (StackOverflow)
I'd like Bundler to load a local gem. Is there an option for that? Or do I have to move the gem folder into the .bundle directory?
Source: (StackOverflow)
Trying to install a gem (gem install mygem) or update RubyGems (gem update --system) fails with this error:
ERROR: While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
Anyone having idea how to solve this?
Source: (StackOverflow)
When I want to create a Ruby on Rails project, I get the message below.
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:55: uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /usr/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support.rb:57
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /usr/lib/ruby/gems/1.8/gems/rails-2.3.8/lib/rails_generator.rb:31
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /usr/lib/ruby/gems/1.8/gems/rails-2.3.8/bin/rails:15
from /usr/bin/rails:19:in `load'
from /usr/bin/rails:19
What has gone wrong? How do I to fix it?
Source: (StackOverflow)
If I download a .gem file to a folder in my computer, can I install it later using gem install?
Source: (StackOverflow)
I don't use the RI or RDoc output from the gems I install in my machine or in the servers I handle (I use other means of documentation).
Every gem I install installs RI and RDoc documentation by default, because I forget to set --no-ri --no-rdoc.
Is there a way to make those two flags the default?
Source: (StackOverflow)
There are instances where I would like to revert and uninstall all previous gem installations.
For instance, I needed to assist a friend migrate their rails development machine to use RVM. As they had been previously using the system-wide gem, he was experiencing many headaches when working with multiple projects. Essentially, he was the poster-child for an RVM convert.
How can I elegantly uninstall all of the gems on his OSX system?
Source: (StackOverflow)
I installed zlib package and ruby 1.9.3 using rvm, but whenever I try to install
gems it says
cannot load such file -- zlib
The commands I used to install are
$ rvm install 1.9.3
$ rvm pkg install zlib
$ rvm reinstall 1.9.3 --with-readline-dir=/home/username/.rvm/usr \
--with-iconv-dir=/home/username/.rvm/usr \
--with-zlib-dir=/home/username/.rvm/usr \
--with-openssl-dir=/home/username/.rvm/usr
$ rvm use 1.9.3
$ gem install heroku
ERROR: Loading command: install (LoadError)
cannot load such file -- zlib
ERROR: While executing gem ... (NameError)
uninitialized constant Gem::Commands::InstallCommand
All the help on this subject tells me to just do rvm pkg install zlib, and
then reinstall the ruby with --with-zlib-dir=/home/username/.rvm/usr, but this
didn't work.
Source: (StackOverflow)
I'm using rails_admin, and since it is in (very) active development, bugs turn up every now and then.
There are no versions for the gem as far as I can tell, for the gem in github, so I can't use the :version key for the gem declaration in the Gemfile .
Is there a way I can "tie" a specific commit(that I know is working fine for me) to the Gemfile ?
I currently have in my Gemfile:
gem 'rails_admin',
:git => 'git://github.com/sferik/rails_admin.git'
I'd like to be able to do something like this (example "commit_id"):
gem 'rails_admin',
:git => 'git://github.com/sferik/rails_admin.git',
:commit_id => "4e7d53e3c5c4c3c5c43c3"
Is this possible to do with github?
Source: (StackOverflow)
I am getting the following error when I try to use gems in windows, and I also referred to
this stackoverflow post and updated rubygems and rails. But nothing could solve the problem.
The following is the complete error,
D:\>gem env
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/tilt-1.3.3.gemspec]: invalid date format in specification: "2011-08-25 00:00:00
.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/execjs-1.2.4.gemspec]: invalid date format in specification: "2011-08-03 00:00:
00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/temple-0.3.3.gemspec]: invalid date format in specification: "2011-08-26 00:00:
00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/guard-0.6.3.gemspec]: invalid date format in specification: "2011-09-01 00:00:0
0.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/guard-livereload-0.3.1.gemspec]: invalid date format in specification: "2011-09
-01 00:00:00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/rack-cache-1.0.3.gemspec]: invalid date format in specification: "2011-08-27 00
:00:00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/tilt-1.3.3.gemspec]: invalid date format in specification: "2011-08-25 00:00:00
.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/execjs-1.2.4.gemspec]: invalid date format in specification: "2011-08-03 00:00:
00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/temple-0.3.3.gemspec]: invalid date format in specification: "2011-08-26 00:00:
00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/guard-0.6.3.gemspec]: invalid date format in specification: "2011-09-01 00:00:0
0.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/guard-livereload-0.3.1.gemspec]: invalid date format in specification: "2011-09
-01 00:00:00.000000000Z"
Invalid gemspec in [D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/specifications
/rack-cache-1.0.3.gemspec]: invalid date format in specification: "2011-08-27 00
:00:00.000000000Z"
RubyGems Environment:
- RUBYGEMS VERSION: 1.7.2
- RUBY VERSION: 1.8.7 (2011-06-30 patchlevel 352) [i386-mingw32]
- INSTALLATION DIRECTORY: D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8
- RUBY EXECUTABLE: D:/RailsInstaller/Ruby1.8.7/bin/ruby.exe
- EXECUTABLE DIRECTORY: D:/RailsInstaller/Ruby1.8.7/bin
- RUBYGEMS PLATFORMS:
- ruby
- x86-mingw32
- GEM PATHS:
- D:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8
- C:/Documents and Settings/jeygokul/.gem/ruby/1.8
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:
- http://rubygems.org/
Source: (StackOverflow)
Ruby 1.9.3
The part of Gemfile
#...............
gem "pony"
gem "bcrypt-ruby", :require => "bcrypt"
gem "nokogiri"
#..................
When I'm trying to install gems, I get an error
alex@ubuntu:~/$ bundle
Fetching gem metadata from http://rubygems.org/.........
Fetching gem metadata from http://rubygems.org/..
Enter your password to install the bundled RubyGems to your system:
#####............................................................
Installing bcrypt-ruby (3.0.1) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from extconf.rb:36:in `<main>'
Gem files will remain installed in /home/alex/.bundler/tmp/5526/gems/bcrypt-ruby-3.0.1 for inspection.
Results logged to /home/alex/.bundler/tmp/5526/gems/bcrypt-ruby-3.0.1/ext/mri/gem_make.out
An error occurred while installing bcrypt-ruby (3.0.1), and Bundler cannot continue.
Make sure that `gem install bcrypt-ruby -v '3.0.1'` succeeds before bundling.
Then I'm doing this
sudo gem install bcrypt-ruby -v '3.0.1'
Building native extensions. This could take a while...
ERROR: Error installing bcrypt-ruby:
ERROR: Failed to build gem native extension.
/usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from extconf.rb:36:in `<main>'
Gem files will remain installed in /var/lib/gems/1.9.1/gems/bcrypt-ruby-3.0.1 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/bcrypt-ruby-3.0.1/ext/mri/gem_make.out
and getting an error as well.
What did I miss?
Source: (StackOverflow)
I'm trying to install PostgreSQL for Rails on Mac OS X 10.6. First I tried the MacPorts install but that didn't go well so I did the one-click DMG install. That seemed to work.
I suspect I need to install the PostgreSQL development packages but I have no idea how to do that on OS X.
Here's what I get when I try to do sudo gem install pg:
$ sudo gem install pg
Building native extensions. This could take a while...
ERROR: Error installing pg:
ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb
checking for pg_config... yes
Using config values from /Library/PostgreSQL/8.3/bin/pg_config
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no
Can't find the PostgreSQL client library (libpq)
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
--with-pg
--without-pg
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pqlib
--without-pqlib
--with-libpqlib
--without-libpqlib
--with-ms/libpqlib
--without-ms/libpqlib
Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/pg-0.11.0 for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/pg-0.11.0/ext/gem_make.out
Source: (StackOverflow)
I use bundler to manage dependencies in my rails app, and I have a gem hosted in a git repository included as followed:
gem 'gem-name', :git => 'path/to/my/gem.git'
To update this gem, I execute bundle update but it also updates all the gem mentioned in Gemfile. So what is the command to update just one specific gem?
Source: (StackOverflow)
I this every time I run rails server:
warning: Insecure world writable dir /usr/local/bin in PATH, mode 040777
I searched for a solution here and they said to type: chmod go-w /usr/local/bin
But I get this error:
chmod: Unable to change file mode on /usr/local/bin: Operation not permitted
I am using OSX by the way.
Source: (StackOverflow)
I am interested in how RVM and RBEnv actually work. Obviously they swap between different versions of Ruby and gemsets, but how is this achieved? I had assumed they were simply updating symlinks, but having delved into the code (and I must admit my knowledge of Bash is superficial) they appear to be doing more than this.
Source: (StackOverflow)