“require”：无法加载文件--mysql2 / mysql2

Question

在安装 mysql2 v 0.4.2 时可能会遇到困难，但是成功后需要使用以下命令：

gem install mysql2 -v '0.4.2' -- --srcdir=/usr/local/mysql/include

当我运行bundle exec rails s时，出现了以下错误：

`require': cannot load such file -- mysql2/mysql2 (LoadError)
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/mysql2-0.4.2/lib/mysql2.rb:31:in `<top (required)>'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler/runtime.rb:82:in `require'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler/runtime.rb:82:in `block (2 levels) in require'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler/runtime.rb:77:in `each'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler/runtime.rb:77:in `block in require'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler/runtime.rb:66:in `each'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler/runtime.rb:66:in `require'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/bundler-1.15.4/lib/bundler.rb:108:in `require'
    from /Users/jmayer/workspace/sekai-property/config/application.rb:8:in `<top (required)>'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:78:in `require'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:78:in `block in server'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `tap'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `server'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
    from /Users/jmayer/.rvm/gems/ruby-2.3.1/gems/railties-4.2.5/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

rails -v
Rails 4.2.5

ruby -v
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin18]

我尝试了stackoverflow上所有与错误相关的内容，但都没有成功。

我只是想启动一个开发服务器，创建一个数据库等。

- Julien

---

我遇到了与Rails 5.2.2 - ruby 2.6.1p33（2019-01-30 revision 66950）[x86_64-darwin18]和mysql2（0.5.2）相同的问题。 bundle exec rails s无法正常工作（我已经在我的gemfile中执行了以下bundle：gem 'mysql2'，'>= 0.4.4'，'<0.6.0'）。 - Jesper Grann Laursen

Answer 1

由于您正在使用 bundle exec，它仅考虑 Gemfile 中存在的 gem，因此您需要将其放在那里。

包括：

gem mysql2 

在您的Gemfile中（位于项目根目录中）

然后运行

bundle install

然后你可以运行

bundle exec rails s

- Paritosh Singh

---

感谢您的回复，不幸的是，我没有列出许多细节。mysql2在gemfile中。在运行gem install...之后，我已经运行了bundle install。此外，我已经在没有bundle exec的情况下运行rails s。 - Julien