我已經安裝了MySQL的寶石，但仍顯示出此錯誤

Question

D:\Projects\Ruby on Rails\Library>rails generate model Book 
     invoke active_record 
C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/active_record/connect 
ion_adapters/connection_specification.rb:177:in `rescue in spec': Specified 'mys 
ql' for database adapter, but the gem is not loaded. Add `gem 'mysql'` to your G 
emfile (and ensure its version is at the minimum required by ActiveRecord). (Gem 
::LoadError) 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/active_r 
ecord/connection_adapters/connection_specification.rb:174:in `spec' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/active_r 
ecord/connection_handling.rb:50:in `establish_connection' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/active_r 
ecord/railtie.rb:120:in `block (2 levels) in <class:Railtie>' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/lazy_load_hooks.rb:38:in `instance_eval' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/lazy_load_hooks.rb:38:in `execute_hook' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/lazy_load_hooks.rb:45:in `block in run_load_hooks' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/lazy_load_hooks.rb:44:in `each' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/lazy_load_hooks.rb:44:in `run_load_hooks' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/active_r 
ecord/base.rb:316:in `<module:ActiveRecord>' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/active_r 
ecord/base.rb:26:in `<top (required)>' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/genera 
tors/named_base.rb:179:in `pluralize_table_names?' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/genera 
tors/named_base.rb:119:in `table_name' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activerecord-4.2.0/lib/rails/ge 
nerators/active_record/model/model_generator.rb:21:in `create_migration_file' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/command.rb 
:27:in `run' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:126:in `invoke_command' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `block in invoke_all' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `each' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `map' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `invoke_all' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/group.rb:2 
32:in `dispatch' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:115:in `invoke' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/group.rb:2 
77:in `block in _invoke_for_class_method' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/shell.rb:6 
8:in `with_padding' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/group.rb:2 
66:in `_invoke_for_class_method' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/group.rb:1 
49:in `_invoke_from_option_orm' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/command.rb 
:27:in `run' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:126:in `invoke_command' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `block in invoke_all' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `each' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `map' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/invocation 
.rb:133:in `invoke_all' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/group.rb:2 
32:in `dispatch' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/thor-0.19.1/lib/thor/base.rb:44 
0:in `start' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/genera 
tors.rb:157:in `invoke' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/comman 
ds/generate.rb:13:in `<top (required)>' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/dependencies.rb:274:in `require' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/dependencies.rb:274:in `block in require' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/dependencies.rb:240:in `load_dependency' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/activesupport-4.2.0/lib/active_ 
support/dependencies.rb:274:in `require' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/comman 
ds/commands_tasks.rb:123:in `require_command!' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/comman 
ds/commands_tasks.rb:130:in `generate_or_destroy' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/comman 
ds/commands_tasks.rb:50:in `generate' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/comman 
ds/commands_tasks.rb:39:in `run_command!' 
     from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-4.2.0/lib/rails/comman 
ds.rb:17:in `<top (required)>' 
     from bin/rails:4:in `require' 

Answer 1

1. 請務必仔細檢查您的Gemfile。

我的Gemfile：

gem 'mysql2', '~> 0.3' 

不要束安裝。

驗證您的database.yml文件。

的database.yml：

development: 
    adapter: mysql2 
    encoding: utf8 
    database: mydatabase 
    username: myusername 
    password: mypass123 
    host: localhost 
    pool: 5 
    port: 3306 
    timeout: 5000 

Answer 2

我有同樣的問題，所有我能得到的是，那裏有與導軌4.2.4從事寶石版本0.4.0一個問題，我所做的解決它是去我的Gemfile，改變寶石版本的MySQL：

gem 'mysql2' 

對於這一個

gem 'mysql2', '~> 0.3.20' 

然後只需運行：

bundle install 

而且它完美

我希望這可能是有用的！