...我们将花一点时间做一个绝对必要的步骤，以确保Active Storage与Heroku一起使用。如果我们添加主密钥（可以在config / master.key中找到），Heroku将只能对您的凭据.yml.enc解密。但是，主键被忽略是有充分理由的。不要将此文件签入git。我们可以使用heroku命令行将密钥秘密添加到我们的heroku配置中。
$ heroku config:set RAILS_MASTER_KEY=<your-master-key-here>我正在尝试将rails应用程序推送到heroku，并遇到与活动存储相关的以下错误：
错误：
undefined method `[]' for nil:NilClass (NoMethodError)
[一切正常，在我的本地计算机上进行开发。我已经运行bundle exec rails active_storage:install，并且与活动存储相关的表已在heroku上成功迁移。但是，当我尝试使用活动存储为数据库添加种子时，会引发错误。当我尝试启动应用程序时，它还会引发heroku控制台。
application.rb：
require 'rails/all'
Gemfile：
gem 'aws-sdk-s3'
config / enviornments / production.rb：
config.active_storage.service = :amazon_dev
credentials.yml：
aws:
access_key_id: XXXXX
secret_access_key: XXXXX
region: XXXXX
bucket: XXXXX
# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
secret_key_base: XXXXX
config / storage.yml：
amazon_dev:
service: S3
access_key_id: <%= Rails.application.credentials.aws[:access_key_id] %>
secret_access_key: <%= Rails.application.credentials.aws[:secret_access_key] %>
region: <%= Rails.application.credentials.aws[:region] %>
bucket: <%= Rails.application.credentials.aws[:bucket] %>
来自heroku consoloe的堆栈跟踪：
Traceback (most recent call last):
83: from bin/rails:9:in `<main>'
82: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `require'
81: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:257:in `load_dependency'
80: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `block in require'
79: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
78: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
77: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
76: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
75: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
74: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/commands.rb:18:in `<top (required)>'
73: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/command.rb:46:in `invoke'
72: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/command/base.rb:65:in `perform'
71: from /app/vendor/bundle/ruby/2.5.0/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
70: from /app/vendor/bundle/ruby/2.5.0/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
69: from /app/vendor/bundle/ruby/2.5.0/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
68: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/commands/console/console_command.rb:95:in `perform'
67: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/command/actions.rb:15:in `require_application_and_environment!'
66: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/command/actions.rb:28:in `require_environment!'
65: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/application.rb:337:in `require_environment!'
64: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `require'
63: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:257:in `load_dependency'
62: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `block in require'
61: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
60: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
59: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
58: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
57: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
56: from /app/config/environment.rb:5:in `<top (required)>'
55: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/application.rb:361:in `initialize!'
54: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/initializable.rb:60:in `run_initializers'
53: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:205:in `tsort_each'
52: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:226:in `tsort_each'
51: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:347:in `each_strongly_connected_component'
50: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:347:in `call'
49: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:347:in `each'
48: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:349:in `block in each_strongly_connected_component'
47: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:431:in `each_strongly_connected_component_from'
46: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
45: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/tsort.rb:228:in `block in tsort_each'
44: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/initializable.rb:61:in `block in run_initializers'
43: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/initializable.rb:32:in `run'
42: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/initializable.rb:32:in `instance_exec'
41: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/application/finisher.rb:69:in `block in <module:Finisher>'
40: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/application/finisher.rb:69:in `each'
39: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/engine.rb:356:in `eager_load!'
38: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/engine.rb:475:in `eager_load!'
37: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/engine.rb:475:in `each'
36: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/engine.rb:477:in `block in eager_load!'
35: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/engine.rb:477:in `each'
34: from /app/vendor/bundle/ruby/2.5.0/gems/railties-5.2.3/lib/rails/engine.rb:478:in `block (2 levels) in eager_load!'
33: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:246:in `require_dependency'
32: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/active_support.rb:85:in `depend_on'
31: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:334:in `depend_on'
30: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/active_support.rb:47:in `require_or_load'
29: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/active_support.rb:16:in `allow_bootsnap_retry'
28: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/active_support.rb:48:in `block in require_or_load'
27: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:356:in `require_or_load'
26: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:37:in `load_interlock'
25: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies/interlock.rb:13:in `loading'
24: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/concurrency/share_lock.rb:151:in `exclusive'
23: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies/interlock.rb:14:in `block in loading'
22: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:37:in `block in load_interlock'
21: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:378:in `block in require_or_load'
20: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `require'
19: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:257:in `load_dependency'
18: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/dependencies.rb:291:in `block in require'
17: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
16: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
15: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
14: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
13: from /app/vendor/bundle/ruby/2.5.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
12: from /app/vendor/bundle/ruby/2.5.0/gems/activestorage-5.2.3/app/models/active_storage/blob.rb:16:in `<top (required)>'
11: from /app/vendor/bundle/ruby/2.5.0/gems/activestorage-5.2.3/app/models/active_storage/blob.rb:235:in `<class:Blob>'
10: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:51:in `run_load_hooks'
9: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:51:in `each'
8: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:52:in `block in run_load_hooks'
7: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:67:in `execute_hook'
6: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:62:in `with_execution_control'
5: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:71:in `block in execute_hook'
4: from /app/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.3/lib/active_support/lazy_load_hooks.rb:71:in `instance_eval'
3: from /app/vendor/bundle/ruby/2.5.0/gems/activestorage-5.2.3/lib/active_storage/engine.rb:95:in `block (2 levels) in <class:Engine>'
2: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/erb.rb:876:in `result'
1: from /app/vendor/ruby-2.5.1/lib/ruby/2.5.0/erb.rb:876:in `eval'
(erb):6:in `<main>': undefined method `[]' for nil:NilClass (NoMethodError)
编辑
进行一些挖掘之后，这是activestorage gem中文件的源代码，该错误似乎来自：
https://github.com/rails/rails/blob/v5.2.3/activestorage/lib/active_storage/engine.rb
因此似乎问题几乎肯定与storage.yml文件有关，但我似乎无法查明是什么。
解决方案>>
稍微修改了storage.yml之后，错误消失了，一切都按预期进行。我怀疑storage.yml文件中有多余的空间，我没有注意到。
<< [...我们将花一点时间做一个绝对必要的步骤，以确保Active Storage与Heroku一起使用。如果我们添加主密钥（可以在config / master.key中找到），Heroku将只能对您的凭据.yml.enc解密。但是，主键被忽略是有充分理由的。不要将此文件签入git。我们可以使用heroku命令行将密钥秘密添加到我们的heroku配置中。
$ heroku config:set RAILS_MASTER_KEY=<your-master-key-here>如果不这样做，则Active Storage在Heroku上将无法使用，并且会导致大量无用的错误。