我正在使用三个辅助方法创建一个 Rails 引擎。一个加载 YAML 配置文件，另一个确定 YAML 配置文件中的选项是否存在，如果存在，则返回 YAML 配置选项的值。否则，它返回 Rails 应用程序名称和字符串':chat'：
def config_file
YAML.load_file(Rails.root.join('config', 'kouventa.yml'))
end
# This helper gets the name of the Rails app you're in.
# It also appends a :chat to it.
def app_name
yaml = config_file
name = Rails.application.class.to_s.split('::').first
if yaml[:app][:name] == true
yaml[:app][:name]
else
"#{name.uncapitalize}:chat"
end
end
问题是，如果我包含<%= app_name %>在我的 ERB 模板中，它会引发以下错误：no implicit conversion from nil to integer
这是完整的跟踪：
/Users/chris/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:297:in `initialize'
/Users/chris/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:297:in `open'
/Users/chris/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:297:in `load_file'
/Users/chris/src/railssrc/kouventa/app/helpers/kouventa/application_helper.rb:4:in `config_file'
/Users/chris/src/railssrc/kouventa/app/helpers/kouventa/application_helper.rb:10:in `app_name'
/Users/chris/src/railssrc/kouventa/app/views/layouts/kouventa/application.html.erb:16:in `___sers_chris_src_railssrc_kouventa_app_views_layouts_kouventa_application_html_erb___3103356657825490294_70127840047660'
actionpack (3.2.11) lib/action_view/template.rb:145:in `block in render'
activesupport (3.2.11) lib/active_support/notifications.rb:125:in `instrument'
actionpack (3.2.11) lib/action_view/template.rb:143:in `render'
actionpack (3.2.11) lib/action_view/renderer/template_renderer.rb:59:in `render_with_layout'
actionpack (3.2.11) lib/action_view/renderer/template_renderer.rb:45:in `render_template'
actionpack (3.2.11) lib/action_view/renderer/template_renderer.rb:18:in `render'
actionpack (3.2.11) lib/action_view/renderer/renderer.rb:36:in `render_template'
actionpack (3.2.11) lib/action_view/renderer/renderer.rb:17:in `render'
actionpack (3.2.11) lib/abstract_controller/rendering.rb:110:in `_render_template'
actionpack (3.2.11) lib/action_controller/metal/streaming.rb:225:in `_render_template'
actionpack (3.2.11) lib/abstract_controller/rendering.rb:103:in `render_to_body'
actionpack (3.2.11) lib/action_controller/metal/renderers.rb:28:in `render_to_body'
actionpack (3.2.11) lib/action_controller/metal/compatibility.rb:50:in `render_to_body'
actionpack (3.2.11) lib/abstract_controller/rendering.rb:88:in `render'
actionpack (3.2.11) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:40:in `block (2 levels) in render'
activesupport (3.2.11) lib/active_support/core_ext/benchmark.rb:5:in `block in ms'
/Users/chris/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/benchmark.rb:295:in `realtime'
activesupport (3.2.11) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:40:in `block in render'
actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:83:in `cleanup_view_runtime'
activerecord (3.2.11) lib/active_record/railties/controller_runtime.rb:24:in `cleanup_view_runtime'
actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:39:in `render'
actionpack (3.2.11) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (3.2.11) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (3.2.11) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.2.11) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.2.11) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.2.11) lib/active_support/callbacks.rb:403:in `_run__1576663026866565057__process_action__3352794237780824881__callbacks'
activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.11) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
activesupport (3.2.11) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.11) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.2.11) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.2.11) lib/active_support/notifications.rb:123:in `block in instrument'
activesupport (3.2.11) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (3.2.11) lib/active_support/notifications.rb:123:in `instrument'
actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.2.11) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
activerecord (3.2.11) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.11) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.11) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.11) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.11) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.11) lib/action_controller/metal.rb:246:in `block in action'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:601:in `call'
railties (3.2.11) lib/rails/engine.rb:479:in `call'
railties (3.2.11) lib/rails/railtie/configurable.rb:30:in `method_missing'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:601:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.4) lib/rack/etag.rb:23:in `call'
rack (1.4.4) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.4) lib/rack/session/abstract/id.rb:210:in `context'
rack (1.4.4) lib/rack/session/abstract/id.rb:205:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/cookies.rb:341:in `call'
activerecord (3.2.11) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `_run__2096171487662296236__call__865153784229083501__callbacks'
activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.11) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.11) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.11) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/reloader.rb:65:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.11) lib/rails/rack/logger.rb:32:in `call_app'
railties (3.2.11) lib/rails/rack/logger.rb:16:in `block in call'
activesupport (3.2.11) lib/active_support/tagged_logging.rb:22:in `tagged'
railties (3.2.11) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.4) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.4) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.11) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.4) lib/rack/lock.rb:15:in `call'
actionpack (3.2.11) lib/action_dispatch/middleware/static.rb:62:in `call'
railties (3.2.11) lib/rails/engine.rb:479:in `call'
railties (3.2.11) lib/rails/application.rb:223:in `call'
railties (3.2.11) lib/rails/railtie/configurable.rb:30:in `method_missing'
unicorn (4.5.0) lib/unicorn/http_server.rb:552:in `process_client'
unicorn (4.5.0) lib/unicorn/http_server.rb:628:in `worker_loop'
unicorn (4.5.0) lib/unicorn/http_server.rb:500:in `spawn_missing_workers'
unicorn (4.5.0) lib/unicorn/http_server.rb:142:in `start'
unicorn (4.5.0) bin/unicorn_rails:209:in `<top (required)>'
/Users/chris/.rvm/gems/ruby-1.9.3-p194/bin/unicorn_rails:19:in `load'
/Users/chris/.rvm/gems/ruby-1.9.3-p194/bin/unicorn_rails:19:in `<main>'
/Users/chris/.rvm/gems/ruby-1.9.3-p194/bin/ruby_noexec_wrapper:14:in `eval'
/Users/chris/.rvm/gems/ruby-1.9.3-p194/bin/ruby_noexec_wrapper:14:in `<main>'