Rails设置：mysql2 gem总是引起问题

Question

I'm fairly new when it comes to commandline or Rails, but work on a rails project where I'm doing the frontend.

I've installed all gems that are needed for the project, but lately some errors occur when doing a rake:db migrate or today when trying to deploy the current version via cap production deploy

The problem I'm facing seems to have todo with the mysql2 gem. At least that is what the console says.

When running cap production deploy I get this error:

rake stdout: Nothing written
rake stderr: rake aborted!
Gem::LoadError: Specified 'mysql2' for database adapter, but the gem is not loaded. Add `gem 'mysql2'` to your Gemfile.

and further down this …

Gem::LoadError: can't activate mysql2 (~> 0.3.10), already activated mysql2-0.4.2. Make sure all dependencies are added to Gemfile.

What do I have todo here? When I do gem list I see that mysql2 is installed.

Thank you, Matt

Answer 1

Rails used to have the mysql2 gem locked down to ~>0.3 in the codebase.

So that is what it looks for but your Gemfile will simply state

gem "mysql2"

Pretty sure they've updated this in the latest release of rails 4 so either:

Update to the latest version of rails 4 or use a specific version of the mysql2 gem

gem "mysql2", "~> 0.3.20"