Gem::LoadError for mysql2 gem, but it's already in Gemfile
If you have this error when upgrading to rails 4.2.4 (also with rails 4.1.5) try using this version of mysql2:
gem 'mysql2', '~> 0.3.18'Apparently mysql2 isn't still compatible with newer version of rails because rails 4.2.4 is pretty new as the time of answering this question by me 8 September 2015 so use the above line in your Gem file and run:
bundle install You should be good to go
It worked for me when I specified a mysql2 gem version before the newest one (0.4.0). For some reason there is a problem with Rails 4.2.4 and that gem 0.4.0. So, to solve the problem I just specified the previous gem released: 0.3.20 and it worked fine for me!
gem 'mysql2', '~> 0.3.20'bundle installYou can check all the gems versions here: https://rubygems.org/gems/mysql2/versions
Change to
gem 'mysql2', '~> 0.3.18'in your Gemfile.
This thread on the official mysql2 Github says to do this. You need to declare that version number if you're rails version 4.x.x.
https://github.com/brianmario/mysql2/issues/675
Then run bundle update mysql2.