首先，我搜索并阅读了所有与我的问题相似的问题，并尝试了所有建议。如果有帮助，以下是一些我正在使用的技术：
继Pragmatic Studios Rails 1课程之后，我安装了ruby 2.5.1和Rails 5.0.0新的捆绑软件检查，并且所有依赖项都满足捆绑软件安装等。
所以现在我有了一个新的Rails应用程序设置，我尝试rails s使用Puma服务器运行该应用程序似乎没有问题，但是当我尝试加载浏览器localhost3000时出现错误：
Gem::LoadError
Specified 'sqlite3' for database adapter, but the gem is not loaded. Add `gem 'sqlite3'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
当我在运行服务器时刷新页面时，出现此错误：
ActiveRecord::ConnectionNotEstablished
No connection pool with id primary found.
我已经检查了gem文件，并在那里找到了sqlite3。我已经重新安装了sqlite3。我已经完成了bundle exec rails服务器。我已经卸载了sqlite3并重新安装。我已经删除了Gemfile.lock文件，并捆绑了install（和exec）。我尝试了所有可以在网上找到的建议。
所以现在我想，也许我的系统搞砸了，我可以使用升级到Mojave的方式。
所以...我创建了一个可启动驱动器，删除了HD，并进行了全新安装。
现在，运行Mojave，并重新安装了上面列出的相同应用。
因此，我运行rails-出现相同的错误！这是我在Gemfile和Gemfile.lock中拥有的内容：
来源' https://rubygems.org '
# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.0.0'
# Use sqlite3 as the database for Active Record
gem 'sqlite3'
# Use Puma as the app server
gem 'puma', '~> 3.0'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# See https://github.com/rails/execjs#readme for more supported runtimes
#gem 'therubyracer', platforms: :ruby
# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'
# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development
group :development, :test do
# Call 'byebug' anywhere in the code to stop execution and get a debugger console
gem 'byebug', platform: :mri
end
group :development do
# Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
gem 'web-console'
gem 'listen', '~> 3.0.5'
# Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
gem 'spring'
gem 'spring-watcher-listen', '~> 2.0.0'
end
# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
----------
GEM
remote: https://rubygems.org/
specs:
actioncable (5.0.7.1)
actionpack (= 5.0.7.1)
nio4r (>= 1.2, < 3.0)
websocket-driver (~> 0.6.1)
actionmailer (5.0.7.1)
actionpack (= 5.0.7.1)
actionview (= 5.0.7.1)
activejob (= 5.0.7.1)
mail (~> 2.5, >= 2.5.4)
rails-dom-testing (~> 2.0)
actionpack (5.0.7.1)
actionview (= 5.0.7.1)
activesupport (= 5.0.7.1)
rack (~> 2.0)
rack-test (~> 0.6.3)
rails-dom-testing (~> 2.0)
rails-html-sanitizer (~> 1.0, >= 1.0.2)
actionview (5.0.7.1)
activesupport (= 5.0.7.1)
builder (~> 3.1)
erubis (~> 2.7.0)
rails-dom-testing (~> 2.0)
rails-html-sanitizer (~> 1.0, >= 1.0.3)
activejob (5.0.7.1)
activesupport (= 5.0.7.1)
globalid (>= 0.3.6)
activemodel (5.0.7.1)
activesupport (= 5.0.7.1)
activerecord (5.0.7.1)
activemodel (= 5.0.7.1)
activesupport (= 5.0.7.1)
arel (~> 7.0)
activesupport (5.0.7.1)
concurrent-ruby (~> 1.0, >= 1.0.2)
i18n (>= 0.7, < 2)
minitest (~> 5.1)
tzinfo (~> 1.1)
arel (7.1.4)
bindex (0.5.0)
builder (3.2.3)
byebug (11.0.0)
coffee-rails (4.2.2)
coffee-script (>= 2.2.0)
railties (>= 4.0.0)
coffee-script (2.4.1)
coffee-script-source
execjs
coffee-script-source (1.12.2)
concurrent-ruby (1.1.4)
crass (1.0.4)
erubis (2.7.0)
execjs (2.7.0)
ffi (1.10.0)
globalid (0.4.2)
activesupport (>= 4.2.0)
i18n (1.5.3)
concurrent-ruby (~> 1.0)
jbuilder (2.8.0)
activesupport (>= 4.2.0)
multi_json (>= 1.2)
jquery-rails (4.3.3)
rails-dom-testing (>= 1, < 3)
railties (>= 4.2.0)
thor (>= 0.14, < 2.0)
listen (3.0.8)
rb-fsevent (~> 0.9, >= 0.9.4)
rb-inotify (~> 0.9, >= 0.9.7)
loofah (2.2.3)
crass (~> 1.0.2)
nokogiri (>= 1.5.9)
mail (2.7.1)
mini_mime (>= 0.1.1)
method_source (0.9.2)
mini_mime (1.0.1)
mini_portile2 (2.4.0)
minitest (5.11.3)
multi_json (1.13.1)
nio4r (2.3.1)
nokogiri (1.10.1)
mini_portile2 (~> 2.4.0)
puma (3.12.0)
rack (2.0.6)
rack-test (0.6.3)
rack (>= 1.0)
rails (5.0.7.1)
actioncable (= 5.0.7.1)
actionmailer (= 5.0.7.1)
actionpack (= 5.0.7.1)
actionview (= 5.0.7.1)
activejob (= 5.0.7.1)
activemodel (= 5.0.7.1)
activerecord (= 5.0.7.1)
activesupport (= 5.0.7.1)
bundler (>= 1.3.0)
railties (= 5.0.7.1)
sprockets-rails (>= 2.0.0)
rails-dom-testing (2.0.3)
activesupport (>= 4.2.0)
nokogiri (>= 1.6)
rails-html-sanitizer (1.0.4)
loofah (~> 2.2, >= 2.2.2)
railties (5.0.7.1)
actionpack (= 5.0.7.1)
activesupport (= 5.0.7.1)
method_source
rake (>= 0.8.7)
thor (>= 0.18.1, < 2.0)
rake (12.3.2)
rb-fsevent (0.10.3)
rb-inotify (0.10.0)
ffi (~> 1.0)
sass (3.7.3)
sass-listen (~> 4.0.0)
sass-listen (4.0.0)
rb-fsevent (~> 0.9, >= 0.9.4)
rb-inotify (~> 0.9, >= 0.9.7)
sass-rails (5.0.7)
railties (>= 4.0.0, < 6)
sass (~> 3.1)
sprockets (>= 2.8, < 4.0)
sprockets-rails (>= 2.0, < 4.0)
tilt (>= 1.1, < 3)
spring (2.0.2)
activesupport (>= 4.2)
spring-watcher-listen (2.0.1)
listen (>= 2.7, < 4.0)
spring (>= 1.2, < 3.0)
sprockets (3.7.2)
concurrent-ruby (~> 1.0)
rack (> 1, < 3)
sprockets-rails (3.2.1)
actionpack (>= 4.0)
activesupport (>= 4.0)
sprockets (>= 3.0.0)
sqlite3 (1.4.0)
thor (0.20.3)
thread_safe (0.3.6)
tilt (2.0.9)
turbolinks (5.2.0)
turbolinks-source (~> 5.2)
turbolinks-source (5.2.0)
tzinfo (1.2.5)
thread_safe (~> 0.1)
uglifier (4.1.20)
execjs (>= 0.3.0, < 3)
web-console (3.7.0)
actionview (>= 5.0)
activemodel (>= 5.0)
bindex (>= 0.4.0)
railties (>= 5.0)
websocket-driver (0.6.5)
websocket-extensions (>= 0.1.0)
websocket-extensions (0.1.3)
PLATFORMS
ruby
DEPENDENCIES
byebug
coffee-rails (~> 4.2)
jbuilder (~> 2.5)
jquery-rails
listen (~> 3.0.5)
puma (~> 3.0)
rails (~> 5.0.0)
sass-rails (~> 5.0)
spring
spring-watcher-listen (~> 2.0.0)
sqlite3
turbolinks (~> 5)
tzinfo-data
uglifier (>= 1.3.0)
web-console
BUNDLED WITH
1.16.6
---------
来自PragmaticStudio的Mike Clark为我解决了这个问题！
嗯，似乎是2月4日发布的sqlite3 v1.4.0 gem的问题。有一个修复程序：
https://github.com/rails/rails/issues/35153
同时，您可以通过将该版本添加到Gemfile中的“ sqlite3”行来回退至v1.3.6，如下所示：
gem“ sqlite3”，“〜> 1.3.6”
然后确保“捆绑安装”。
无论如何，这为我解决了这个问题。我还发现这很有帮助：
试试看，看看它是否适合您。
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