Gem::LoadError: Specified 'mysql' for database adapter, but the gem is not loaded. Add `gem 'mysql'` to your Gemfile.

我在遵循本指南时遇到此错误: http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html 并运行

$ cd activerecord
$ bundle exec rake test_sqlite3

搜索了一下后，我被告知需要修改 Gemfile 并添加 gem 'mysql' 然后运行 ​​bundle install。但是，我无法在列表中看到 mysql。

Resolving dependencies...
Using rake (10.1.0) 
Using i18n (0.6.5) 
Using json (1.8.0) 
Using minitest (5.0.8) 
Using atomic (1.1.14) 
Using thread_safe (0.1.3) 
Using tzinfo (0.3.38) 
Using activesupport (4.1.0.beta) from source at . 
Using rack (1.5.2) 
Using rack-test (0.6.2) 
Using actionpack (4.1.0.beta) from source at . 
Using builder (3.1.4) 
Using activemodel (4.1.0.beta) from source at . 
Using erubis (2.7.0) 
Using actionview (4.1.0.beta) from source at . 
Using mime-types (1.25) 
Using polyglot (0.3.3) 
Using treetop (1.4.15) 
Using mail (2.5.4) 
Using actionmailer (4.1.0.beta) from source at . 
Using arel (4.0.0) 
Using activerecord (4.1.0.beta) from source at . 
Using bcrypt-ruby (3.1.2) 
Using benchmark-ips (1.2.0) 
Using bundler (1.3.5) 
Using coffee-script-source (1.6.3) 
Using execjs (2.0.2) 
Using coffee-script (2.2.0) 
Using thor (0.18.1) 
Using railties (4.1.0.beta) from source at . 
Using coffee-rails (4.0.0) 
Using columnize (0.3.6) 
Using dalli (2.6.4) 
Using debugger-linecache (1.2.0) 
Using debugger-ruby_core_source (1.2.3) 
Using debugger (1.6.2) 
Using hike (1.2.3) 
Using jquery-rails (2.2.2) 
Using mustache (0.99.4) 
Using mini_portile (0.5.1) 
Using nokogiri (1.6.0) 
Using kindlerb (0.1.1) 
Using metaclass (0.0.1) 
Using mocha (0.14.0) 
Using multi_json (1.8.1) 
Using racc (1.4.9) 
Using rack-cache (1.2) 
Using tilt (1.4.1) 
Using sprockets (2.10.0) 
Using sprockets-rails (2.0.0) 
Using rails (4.1.0.beta) from source at . 
Using rdoc (3.12.2) 
Using redcarpet (2.2.2) 
Using sdoc (0.3.20) 
Using sqlite3 (1.3.8) 
Using turbolinks (1.3.0) 
Using uglifier (2.2.1) 
Using w3c_validators (1.2) 
Using yajl-ruby (1.1.0) 
Your bundle is complete!
Gems in the group db were not installed.
Use `bundle show [gemname]` to see where a bundled gem is installed.

gem 文件

source 'https://rubygems.org'

gem 'rails',     path: '/home/terence/rails'
gem 'arel',      github: 'rails/arel'

gem 'mysql', '~> 2.9.1'
gem 'mysql2', '~> 0.3.13'

# Use sqlite3 as the database for Active Record
gem 'sqlite3'

# Use edge version of sprockets-rails
gem 'sprockets-rails', github: 'rails/sprockets-rails'

# Use SCSS for stylesheets
gem 'sass-rails', github: 'rails/sass-rails'

# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'

# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', github: 'rails/coffee-rails'

# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'

# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'

# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 1.2'

# Run `rails console` in the browser. Read more: https://github.com/rails/web-console
gem 'web-console', group: :development

group :doc do
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', require: false
end

# Use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.1.2'

# Use unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano', group: :development

# Use debugger
# gem 'debugger', group: [:development, :test]

但是，如果我运行 gem list，我的输出如下:

*** LOCAL GEMS ***

actionmailer (4.0.0)
actionpack (4.0.0)
activemodel (4.0.0)
activerecord (4.0.0)
activerecord-deprecated_finders (1.0.3)
activesupport (4.0.0)
arel (4.0.0)
atomic (1.1.14)
bcrypt-ruby (3.1.2)
benchmark-ips (1.2.0)
builder (3.1.4)
bundler (1.3.5)
bundler-unload (1.0.2)
celluloid (0.15.2)
chunky_png (1.2.8)
coderay (1.0.9)
coffee-rails (4.0.0)
coffee-script (2.2.0)
coffee-script-source (1.6.3)
columnize (0.3.6)
compass (0.12.2)
cyaml (0.0.45)
dalli (2.6.4)
debugger (1.6.2)
debugger-linecache (1.2.0)
debugger-ruby_core_source (1.2.3)
em-websocket (0.5.0)
erubis (2.7.0)
eventmachine (1.0.3)
execjs (2.0.2)
executable-hooks (1.2.3)
ffi (1.9.0)
formatador (0.2.4)
fssm (0.2.10)
guard (2.0.3)
guard-compass (1.0.0)
guard-haml (1.1.0)
guard-livereload (2.0.0)
haml (4.0.3)
hike (1.2.3)
http_parser.rb (0.5.3)
i18n (0.6.5)
jbuilder (1.5.1)
jquery-rails (3.0.4, 2.2.2)
json (1.8.0)
kindlerb (0.1.1)
listen (2.0.1)
lumberjack (1.0.4)
mail (2.5.4)
metaclass (0.0.1)
method_source (0.8.2)
mime-types (1.25)
mini_portile (0.5.1)
minitest (5.0.8, 4.7.5)
mocha (0.14.0)
multi_json (1.8.1)
mustache (0.99.4)
mysql (2.9.1)
mysql2 (0.3.13)
nokogiri (1.6.0)
polyglot (0.3.3)
pry (0.9.12.2)
racc (1.4.9)
rack (1.5.2)
rack-cache (1.2)
rack-test (0.6.2)
rails (4.0.0)
railties (4.0.0)
rake (10.1.0)
rb-fsevent (0.9.3)
rb-inotify (0.9.2)
rdoc (3.12.2)
redcarpet (2.2.2)
rubygems-bundler (1.3.4)
rvm (1.11.3.8)
sass (3.2.12)
sass-rails (4.0.0)
sdoc (0.3.20)
slop (3.4.6)
sprockets (2.10.0)
sprockets-rails (2.0.0)
sqlite3 (1.3.8)
thor (0.18.1)
thread_safe (0.1.3)
tilt (1.4.1)
timers (1.1.0)
treetop (1.4.15)
turbolinks (1.3.0)
tzinfo (0.3.38, 0.3.37)
uglifier (2.2.1)
w3c_validators (1.2)
web-console (1.0.3)
yajl-ruby (1.1.0)

数据库.yml

# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
development:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

production:
  adapter: sqlite3
  database: db/production.sqlite3
  pool: 5
  timeout: 5000

请帮忙？

最佳答案

我发现了导致此错误的另一个原因。当我安装了 mysql2 gem 时，在我的模型中我指定了字符串“mysql”来建立连接:

establish_connection adapter: "mysql", database: "my_database"

很明显，应该是“mysql2”而不是“mysql”。

关于mysql - Gem::LoadError: 添加 `gem ' mysql'` 到你的 Gemfile，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19260147/