无法激活mysql2 (~> 0.3.10)，已激活mysql2-0.4.3

Question

在运行rails应用程序时，我得到了以下错误-

DEPRECATION WARNING: Support for Rails < 4.1.0 will be dropped. (called from warn at /home/user/.rvm/rubies/ruby-2.1.6/lib/ruby/2.1.0/forwardable.rb:183)
/home/user/.rvm/gems/ruby-2.1.6/gems/signalfx-0.1.0/lib/signalfx/conf.rb:3:in `<top (required)>': Use RbConfig instead of obsolete and deprecated Config.
/home/user/.rvm/gems/ruby-2.1.6/gems/bundler-1.11.2/lib/bundler/rubygems_integration.rb:314:in `block in replace_gem': Please install the mysql2 adapter: `gem install activerecord-mysql2-adapter` (can't activate mysql2 (~> 0.3.10), already activated mysql2-0.4.3. Make sure all dependencies are added to Gemfile.) (LoadError)
    from /home/user/.rvm/gems/ruby-2.1.6/gems/activerecord-3.2.17/lib/active_record/connection_adapters/mysql2_adapter.rb:3:in `<top (required)>'
    from /home/user/.rvm/gems/ruby-2.1.6/gems/activesupport-3.2.17/lib/active_support/dependencies.rb:251:in `require'
    from /home/user/.rvm/gems/ruby-2.1.6/gems/activesupport-3.2.17/lib/active_support/dependencies.rb:251:in `block in require'
    from /home/user/.rvm/gems/ruby-2.1.6/gems/activesupport-3.2.17/lib/active_support/dependencies.rb:236:in `load_dependency'
    from /home/user/.rvm/gems/ruby-2.1.6/gems/activesupport-3.2.17/lib/active_support/dependencies.rb:251:in `require'

在the文件中，我有一个条目：gem 'mysql2', '~> 0.3'

检查安装了哪个gem：

$ gem list|grep mysql2

activerecord-mysql2-adapter (0.0.3)
mysql2 (0.4.3)

如何解决此错误？

Answer 1

更新Gemfile，指定确切的版本

gem 'mysql2', '0.3.20'

那就跑

bundle update mysql2

这将使用Gemfile的版本更新您的mysql2宝石。

Answer 2

通常可以通过在命令前面加上bundle exec来避免这种情况--这将确保命令在绑定的gems的上下文中运行，而不是在系统gems的上下文中运行。

如果您为多个项目执行bundle install，但不设置部署路径或为单个项目分离已安装的gems，则可能发生这种情况。

例如bundle exec rails s