I\'m a complete n00b on Rails with only beginner knowledge of Ruby. I plan on studying Ruby more before I really learn Rails, but I\'m waayy too curious for my own good.
In my case, this error "Specified 'sqlite3' for database adapter, but the gem is not loaded. Add gem 'sqlite3' to your Gemfile."
message showed up, when I ran rails server
right after I generated a fresh rails app. It was with Rails version 4.1.16 (Ruby version 2.3.1)
gem 'sqlite3', '~> 1.3.0'
This line in Gemfile removed the error message. I think new sqlite gem (version 1.4) has a conflict with old rails (version 4.1) but I didn't see any related issue on their Github repository. I'm adding this answer here because it might help anybody experiencing the same situation I'm in.