我是一名中级 Rails 开发人员，我在生产环境中使用远程数据库作为我的唯一连接。我的堆栈是 Rails 5 和 Ruby 2.4.0。我已经为数据库设置了环境变量，例如用户名和密码。当我部署到 Heroku 时，我收到以下错误消息：
Cannot load `Rails.application.database_configuration`: (NoMethodError)
undefined method `[]' for nil:NilClass
我假设这是因为 Rails 看不到环境变量，但即使我硬编码了数据库的用户名和密码以进行测试，也会发生相同的错误。
这是我的数据库.yml
default: &default
adapter: mysql2
encoding: utf8
pool: 5
socket: /tmp/mysql.sock
reconnect: true
development:
<<: *default
database: hittrax_tournaments_development
username: root
password: <%= ENV['DB_PASSWORD'] %>
test:
<<: *default
database: hittrax_tournaments_test
username: root
password: <%= Rails.application.secrets[:database][:password] %>
production:
adapter: mysql2
database: <%= ENV['DATABASE'] %>
username: <%= ENV['USERNAME'] %>
password: <%= ENV['PASSWORD'] %>
host: <%= ENV['HOST'] %>
port: 3306
这是堆栈跟踪
/app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/xml_mini.rb:51: warning: constant ::Fixnum is deprecated
/app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/xml_mini.rb:52: warning: constant ::Bignum is deprecated
/app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/core_ext/numeric/conversions.rb:138: warning: constant ::Fixnum is deprecated
(erb):12:in `<main>': Cannot load `Rails.application.database_configuration`: (NoMethodError)
undefined method `[]' for nil:NilClass
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/erb.rb:896:in `eval'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/erb.rb:896:in `result'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application/configuration.rb:137:in `database_configuration'
from /app/vendor/bundle/ruby/2.4.0/gems/activerecord-5.0.1/lib/active_record/railtie.rb:122:in `block (2 levels) in <class:Railtie>'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:43:in `instance_eval'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:43:in `execute_hook'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:49:in `each'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
from /app/vendor/bundle/ruby/2.4.0/gems/activerecord-5.0.1/lib/active_record/base.rb:324:in `<module:ActiveRecord>'
from /app/vendor/bundle/ruby/2.4.0/gems/activerecord-5.0.1/lib/active_record/base.rb:24:in `<top (required)>'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /app/app/models/application_record.rb:1:in `<top (required)>'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:380:in `block in require_or_load'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:37:in `block in load_interlock'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies/interlock.rb:12:in `block in loading'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/concurrency/share_lock.rb:150:in `exclusive'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies/interlock.rb:11:in `loading'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:37:in `load_interlock'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:358:in `require_or_load'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:336:in `depend_on'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:252:in `require_dependency'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:476:in `block (2 levels) in eager_load!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:475:in `each'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:475:in `block in eager_load!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:473:in `each'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:473:in `eager_load!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:354:in `eager_load!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application/finisher.rb:59:in `each'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application/finisher.rb:59:in `block in <module:Finisher>'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:30:in `instance_exec'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:30:in `run'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:55:in `block in run_initializers'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:228:in `block in tsort_each'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:431:in `each_strongly_connected_component_from'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:349:in `block in each_strongly_connected_component'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:347:in `each'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:347:in `call'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:347:in `each_strongly_connected_component'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:226:in `tsort_each'
from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:205:in `tsort_each'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:54:in `run_initializers'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application.rb:352:in `initialize!'
from /app/config/environment.rb:5:in `<top (required)>'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application.rb:328:in `require_environment!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:157:in `require_application_and_environment!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:77:in `console'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands.rb:18:in `<top (required)>'
from /app/bin/rails:9:in `require'
from /app/bin/rails:9:in `<main>'
谢谢！
问题来自test环境部分中的这一行：
<%= Rails.application.secrets[:database][:password] %>
当 Rails 启动时，它会加载config/database.yml并在YAML.load之前使用 ERB gem 解析整个文件。因此，无论您运行哪个环境，每个 erb 代码都将被执行。当 ERB 解析器来到上面的行时，它会:password尝试从 Rails.application.secrets[:database] .当相应的环境键下没有:database部分时，Rails.application.secrets[:database]会变得nil，对其调用[:password]会给你错误
undefined method `[]' for nil:NilClass
您可以在config/secrets.yml中的每个环境键下添加database:来解决此问题。或者用扁平结构secrets[:database_password]替换嵌套的secrets[:database][:password]结构。或删除导致问题的行。
您可以在/railties-5.1.4/lib/rails/application/configuration.rb中查看database_configuration方法以获取更多详细信息。
在处理 YAML 文件格式时，缩进很重要。您有几个不同的缩进级别。
此外，您似乎缺少"测试"环境的密钥。
default: &default
adapter: mysql2
encoding: utf8
pool: 5
socket: /tmp/mysql.sock
reconnect: true
development:
<<: *default
database: hittrax_tournaments_development
username: root
password: <%= ENV['DB_PASSWORD'] %>
test:
<<: *default
database: hittrax_tournaments_test
username: root
password: <%= Rails.application.secrets[:database][:password] %>
production:
database: <%= ENV['DATABASE'] %>
username: <%= ENV['USERNAME'] %>
password: <%= ENV['PASSWORD'] %>
host: <%= ENV['HOST'] %>
port: 3306
另外，作为参考，这是我在运行rails new hittrax -d mysql时得到的：
default: &default
adapter: mysql2
encoding: utf8
pool: 5
username: root
password:
socket: /tmp/mysql.sock
development:
<<: *default
database: hittrax_development
test:
<<: *default
database: hittrax_test
production:
<<: *default
database: hittrax_production
username: hittrax
password: <%= ENV['HITTRAX_DATABASE_PASSWORD'] %>