Gem :: LoadError：将`gem'mysql'添加到你的Gemfile中

Question

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 并且正在运行

$ cd activerecord
$ bundle exec rake test_sqlite3

在搜索了一下之后，我被告知我需要修改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.

的Gemfile

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)

的database.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

请帮忙吗？

Answer 1

我发现了此错误的另一个原因。虽然我安装了mysql2 gem，但在我的模型中我将字符串“mysql”指定为establish_connection：

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

显然，它应该是“mysql2”而不是“mysql”。

Answer 2

已解决：这花了我一段时间才弄明白，我责怪导游的错。无论如何，请确保您正在编辑正确的Gemfile，并在包含您更改的bundle install的目录中执行Gemfile。我跑的时候

$ cd rails
$ bundle exec rails new ~/my-test-app --dev

实际上在我的主目录中创建了一个名为my-test-app的文件夹（其中包含一个Gemfile），但是我必须在我的rails目录中运行$ bundle exec rake test_sqlite3（它还包含一个Gemfile）。

查看上面的输出，当我运行Gems in the group db were not installed.并且指的是bundle install中没有执行的行时，它说Gemfile，他们恰好是安装mysql，mysql2和postgresql的gem行。我纠正了这个文件：

<强>的Gemfile

  # AR
  gem 'sqlite3', '~> 1.3.6'
  gem 'mysql', '~> 2.9.1'
  gem 'mysql2', '~> 0.3.13'
  gem 'pg', '~> 0.17.0'

  group :db do
#    gem 'pg', '>= 0.11.0'
#    gem 'mysql', '>= 2.9.0'
#    gem 'mysql2', '>= 0.3.13'
  end

Answer 3

我遇到了同样的问题。解决方案是我忘了相应地调整Gemfile。因此，切换到您创建rails应用程序的目录，然后使用#include <iostream> #include <Windows.h> const DWORD transparenton = 0x00000001; const DWORD transparentoff = 0x00000000; using namespace std; void pause(); void act(HKEY key); bool getTransparency(HKEY key, DWORD &value); void setTransparency(HKEY key, DWORD value); int main() { cout << "\tStart Menu Blurrier\n"; cout << "Make your Windows 10 start menu background blurry like in Windows 7\nAutomatic On/Off\n"; pause(); HKEY hKey; LONG result = RegOpenKeyExW(HKEY_CURRENT_USER, L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", 0, KEY_QUERY_VALUE | KEY_SET_VALUE, &hKey); if (result == 0) { act(hKey); RegCloseKey(hKey); } return 0; } void pause() { cout << "Press [ENTER] to continue..."; cin.get(); system("cls"); } void act(HKEY key) { DWORD value; if (getTransparency(key, value)) { if (value == transparenton) { setTransparency(key, transparentoff); } else { setTransparency(key, transparenton); } } } bool getTransparency(HKEY key, DWORD &value) { DWORD size = sizeof(value); LONG result = RegQueryValueExW(key, L"EnableBlurBehind", NULL, NULL, (BYTE*)&value, &size); if (result == ERROR_FILE_NOT_FOUND) { value = transparentoff; result = 0; } return (result == 0); } void setTransparency(HKEY key, DWORD value) { RegSetValueExW(key, L"EnableBlurBehind", 0, REG_DWORD, (BYTE*)&value, sizeof(value)); } 打开Gemfile。 在那里你必须根据你的需要添加或删除某些宝石。 在我的情况下，我不得不用“mysql”交换db-gem“sqlite3”。 之后，使用sudo vim Gemfile保存文件并再次运行:wq。

这对我来说已经完成了这项工作，希望它对你们有些帮助！