flash.delete(:notice) not working in Rails 3.1 RC?

Question

A few months ago, I followed this tutorial. Everything worked in Rails 3.0.X, but in Rails 3.1 RC, I get this error:

undefined method `gsub' for #<ActionDispatch::Flash::FlashHash:0x00000108338f20>

Has anything changed in Rails 3.1 RC with the flash object? It seems the problem is with this line:

<%= escape_javascript(flash.delete(:notice)) %>

Full trace:

actionpack (3.1.0.rc1) lib/action_view/helpers/javascript_helper.rb:21:in `escape_javascript'
app/views/likes/create.js.erb:4:in `_app_views_likes_create_js_erb___2491329848991146022_2217047840'
actionpack (3.1.0.rc1) lib/action_view/template.rb:144:in `block in render'
activesupport (3.1.0.rc1) lib/active_support/notifications.rb:57:in `instrument'
actionpack (3.1.0.rc1) lib/action_view/template.rb:142:in `render'
actionpack (3.1.0.rc1) lib/action_view/renderer/template_renderer.rb:40:in `block (2 levels) in render_template'
actionpack (3.1.0.rc1) lib/action_view/renderer/abstract_renderer.rb:33:in `block in instrument'
activesupport (3.1.0.rc1) lib/active_support/notifications.rb:55:in `block in instrument'
activesupport (3.1.0.rc1) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.0.rc1) lib/active_support/notifications.rb:55:in `instrument'
actionpack (3.1.0.rc1) lib/action_view/renderer/abstract_renderer.rb:33:in `instrument'
actionpack (3.1.0.rc1) lib/action_view/renderer/template_renderer.rb:39:in `block in render_template'
actionpack (3.1.0.rc1) lib/action_view/renderer/template_renderer.rb:47:in `render_with_layout'
actionpack (3.1.0.rc1) lib/action_view/renderer/template_renderer.rb:38:in `render_template'
actionpack (3.1.0.rc1) lib/action_view/renderer/template_renderer.rb:12:in `block in render'
actionpack (3.1.0.rc1) lib/action_view/renderer/abstract_renderer.rb:22:in `wrap_formats'
actionpack (3.1.0.rc1) lib/action_view/renderer/template_renderer.rb:9:in `render'
actionpack (3.1.0.rc1) lib/action_view/renderer/renderer.rb:36:in `render_template'
actionpack (3.1.0.rc1) lib/action_view/renderer/renderer.rb:17:in `render'
actionpack (3.1.0.rc1) lib/abstract_controller/rendering.rb:120:in `_render_template'
actionpack (3.1.0.rc1) lib/action_controller/metal/streaming.rb:258:in `_render_template'
actionpack (3.1.0.rc1) lib/abstract_controller/rendering.rb:114:in `render_to_body'
actionpack (3.1.0.rc1) lib/action_controller/metal/renderers.rb:30:in `render_to_body'
actionpack (3.1.0.rc1) lib/action_controller/metal/compatibility.rb:43:in `render_to_body'
actionpack (3.1.0.rc1) lib/abstract_controller/rendering.rb:99:in `render'
actionpack (3.1.0.rc1) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (3.1.0.rc1) lib/action_controller/metal/instrumentation.rb:40:in `block (2 levels) in render'
activesupport (3.1.0.rc1) lib/active_support/core_ext/benchmark.rb:5:in `block in ms'
/Users/Chris/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/benchmark.rb:309:in `realtime'
activesupport (3.1.0.rc1) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.1.0.rc1) lib/action_controller/metal/instrumentation.rb:40:in `block in render'
actionpack (3.1.0.rc1) lib/action_controller/metal/instrumentation.rb:78:in `cleanup_view_runtime'
activerecord (3.1.0.rc1) lib/active_record/railties/controller_runtime.rb:24:in `cleanup_view_runtime'
actionpack (3.1.0.rc1) lib/action_controller/metal/instrumentation.rb:39:in `render'
actionpack (3.1.0.rc1) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (3.1.0.rc1) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (3.1.0.rc1) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.1.0.rc1) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.1.0.rc1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.1.0.rc1) lib/active_support/callbacks.rb:452:in `_run__308249102964749222__process_action__3107984421769475816__callbacks'
activesupport (3.1.0.rc1) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks'
activesupport (3.1.0.rc1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.0.rc1) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.1.0.rc1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.1.0.rc1) lib/active_support/notifications.rb:55:in `block in instrument'
activesupport (3.1.0.rc1) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.0.rc1) lib/active_support/notifications.rb:55:in `instrument'
actionpack (3.1.0.rc1) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.1.0.rc1) lib/action_controller/metal/params_wrapper.rb:202:in `process_action'
actionpack (3.1.0.rc1) lib/action_controller/metal/rescue.rb:17:in `process_action'
activerecord (3.1.0.rc1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.1.0.rc1) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.1.0.rc1) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.1.0.rc1) lib/action_controller/metal.rb:193:in `dispatch'
actionpack (3.1.0.rc1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.1.0.rc1) lib/action_controller/metal.rb:236:in `block in action'
actionpack (3.1.0.rc1) lib/action_dispatch/routing/route_set.rb:65:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/routing/route_set.rb:65:in `dispatch'
actionpack (3.1.0.rc1) lib/action_dispatch/routing/route_set.rb:29:in `call'
rack-mount (0.8.1) lib/rack/mount/route_set.rb:152:in `block in call'
rack-mount (0.8.1) lib/rack/mount/code_generation.rb:93:in `block in recognize'
rack-mount (0.8.1) lib/rack/mount/code_generation.rb:82:in `optimized_each'
rack-mount (0.8.1) lib/rack/mount/code_generation.rb:92:in `recognize'
rack-mount (0.8.1) lib/rack/mount/route_set.rb:141:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/routing/route_set.rb:531:in `call'
/Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/bundler/gems/omniauth-795d965b8961/oa-core/lib/omniauth/strategy.rb:44:in `call!'
/Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/bundler/gems/omniauth-795d965b8961/oa-core/lib/omniauth/strategy.rb:30:in `call'
warden (1.0.4) lib/warden/manager.rb:35:in `block in call'
warden (1.0.4) lib/warden/manager.rb:34:in `catch'
warden (1.0.4) lib/warden/manager.rb:34:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.3.0) lib/rack/etag.rb:23:in `call'
rack (1.3.0) lib/rack/conditionalget.rb:35:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/flash.rb:243:in `call'
rack (1.3.0) lib/rack/session/abstract/id.rb:195:in `context'
rack (1.3.0) lib/rack/session/abstract/id.rb:190:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/cookies.rb:321:in `call'
activerecord (3.1.0.rc1) lib/active_record/query_cache.rb:54:in `call'
activerecord (3.1.0.rc1) lib/active_record/connection_adapters/abstract/connection_pool.rb:448:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (3.1.0.rc1) lib/active_support/callbacks.rb:392:in `_run_call_callbacks'
activesupport (3.1.0.rc1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/reloader.rb:68:in `call'
rack (1.3.0) lib/rack/sendfile.rb:102:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.1.0.rc1) lib/rails/rack/logger.rb:13:in `call'
rack (1.3.0) lib/rack/methodoverride.rb:24:in `call'
rack (1.3.0) lib/rack/runtime.rb:17:in `call'
activesupport (3.1.0.rc1) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.3.0) lib/rack/lock.rb:34:in `call'
actionpack (3.1.0.rc1) lib/action_dispatch/middleware/static.rb:53:in `call'
railties (3.1.0.rc1) lib/rails/rack/content_length.rb:16:in `call'
railties (3.1.0.rc1) lib/rails/engine.rb:438:in `call'
railties (3.1.0.rc1) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.3.0) lib/rack/handler/webrick.rb:59:in `service'
/Users/Chris/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
/Users/Chris/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
/Users/Chris/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'

Answer 1

The FlashHash has changed between 3.0.x and 3.1.x.

In Rails 3.0.x, FlashHash was derived from Hash. Thus when you called delete, it was Hash's delete called - which deletes the specified key and returns the key's value.

In Rails 3.1, FlashHash is not derived from Hash - it is including Enumerable. And the FlashHash#delete is returning self i.e. FlashHash. Thus, your error.

Why the Rails team needed to change this, is beyond me.

I guess you need a workaround that works in both 3.0.x and 3.1:

escape_javascript(flash[:notice])
flash[:notice] = nil

Answer 2

Use flash.discard(:notice)

(Courtesy Christian, I added this solution for better visibility)