title: YAML & Rails: no implicit conversion from nil to integer
body: <p>I'm creating a Rails engine with three helper methods. One loads the YAML config file, and the other determines if an option in the YAML config file exists, and if it does, returns the value of the YAML config option instead. Otherwise, it returns the Rails application name combined with the string <code>':chat'</code>:</p>
  
  <pre><code>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
  </code></pre>
  
  <p>The problem is, if I include <code>&lt;%= app_name %&gt;</code> in my ERB template, it raises the following error: <code>no implicit conversion from nil to integer</code></p>
  
  <p>Here's the full trace:</p>
  
  <pre><code>/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 `&lt;top (required)&gt;'
  /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 `&lt;main&gt;'
  /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 `&lt;main&gt;'
  </code></pre>