delayed_job：未定義方法`name'爲零：NilClass

Question

我剛剛在我的小Rails 3.2應用程序中安裝了延遲作業。這裏是我用它的控制器：

require 'waveform' 

class MixesController < ApplicationController 
    def index 
    end 

    def new 
    @mix = Mix.new 
    end 

    def create 
    @mix = Mix.new(params[:mix]) 
    if @mix.save 
     options = { 
     method: :rms, 
     width: 1800, 
     height: 280, 
     background_color: "#ffffff", 
     color: "#3333ff", 
     force: true, 
     quiet: true 
     } 

     waveform = "./public/waveforms/#{File.basename(@mix.sound_file.to_s, File.extname(@mix.sound_file.to_s))}.png" 
     ::Waveform.new("./public" + @mix.sound_file.to_s, nil).delay.generate(waveform, options) 

     flash[:success] = "Mix successfully uploaded" 
     redirect_to mix_url(@mix) 
    else 
     render :new 
    end 
    end 

    def show 
    @mix = Mix.find(params[:id]) 
    end 
end 

我得到一個錯誤說：undefined method名」的零：NilClass`，以下是完整的堆棧跟蹤：

/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:25:in `block in initialize' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `yield' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `default' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:27:in `block in initialize' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `yield' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `default' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `accept' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:447:in `block in dump_ivars' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:445:in `each' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:445:in `dump_ivars' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:124:in `visit_Object' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:102:in `accept' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:434:in `block in emit_coder' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:432:in `each' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:432:in `emit_coder' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:417:in `dump_coder' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:100:in `accept' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/visitors/yaml_tree.rb:66:in `push' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych.rb:242:in `dump' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/psych/core_ext.rb:14:in `psych_to_yaml' 
delayed_job (3.0.3) lib/delayed/backend/base.rb:80:in `payload_object=' 
activerecord (3.2.3) lib/active_record/attribute_assignment.rb:85:in `block in assign_attributes' 
activerecord (3.2.3) lib/active_record/attribute_assignment.rb:78:in `each' 
activerecord (3.2.3) lib/active_record/attribute_assignment.rb:78:in `assign_attributes' 
activerecord (3.2.3) lib/active_record/base.rb:498:in `initialize' 
delayed_job (3.0.3) lib/delayed/backend/base.rb:28:in `new' 
delayed_job (3.0.3) lib/delayed/backend/base.rb:28:in `enqueue' 
delayed_job (3.0.3) lib/delayed/message_sending.rb:13:in `method_missing' 
app/controllers/mixes_controller.rb:25:in `create' 
actionpack (3.2.3) lib/action_controller/metal/implicit_render.rb:4:in `send_action' 
actionpack (3.2.3) lib/abstract_controller/base.rb:167:in `process_action' 
actionpack (3.2.3) lib/action_controller/metal/rendering.rb:10:in `process_action' 
actionpack (3.2.3) lib/abstract_controller/callbacks.rb:18:in `block in process_action' 
activesupport (3.2.3) lib/active_support/callbacks.rb:414:in `_run__842168672059661955__process_action__4066633601342968686__callbacks' 
activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `__run_callback' 
activesupport (3.2.3) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks' 
activesupport (3.2.3) lib/active_support/callbacks.rb:81:in `run_callbacks' 
actionpack (3.2.3) lib/abstract_controller/callbacks.rb:17:in `process_action' 
actionpack (3.2.3) lib/action_controller/metal/rescue.rb:29:in `process_action' 
actionpack (3.2.3) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action' 
activesupport (3.2.3) lib/active_support/notifications.rb:123:in `block in instrument' 
activesupport (3.2.3) lib/active_support/notifications/instrumenter.rb:20:in `instrument' 
activesupport (3.2.3) lib/active_support/notifications.rb:123:in `instrument' 
actionpack (3.2.3) lib/action_controller/metal/instrumentation.rb:29:in `process_action' 
actionpack (3.2.3) lib/action_controller/metal/params_wrapper.rb:205:in `process_action' 
activerecord (3.2.3) lib/active_record/railties/controller_runtime.rb:18:in `process_action' 
actionpack (3.2.3) lib/abstract_controller/base.rb:121:in `process' 
actionpack (3.2.3) lib/abstract_controller/rendering.rb:45:in `process' 
actionpack (3.2.3) lib/action_controller/metal.rb:203:in `dispatch' 
actionpack (3.2.3) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch' 
actionpack (3.2.3) lib/action_controller/metal.rb:246:in `block in action' 
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:73:in `call' 
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:73:in `dispatch' 
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:36:in `call' 
journey (1.0.3) lib/journey/router.rb:68:in `block in call' 
journey (1.0.3) lib/journey/router.rb:56:in `each' 
journey (1.0.3) lib/journey/router.rb:56:in `call' 
actionpack (3.2.3) lib/action_dispatch/routing/route_set.rb:600:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' 
rack (1.4.1) lib/rack/etag.rb:23:in `call' 
rack (1.4.1) lib/rack/conditionalget.rb:35:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/head.rb:14:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/params_parser.rb:21:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/flash.rb:242:in `call' 
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context' 
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/cookies.rb:338:in `call' 
activerecord (3.2.3) lib/active_record/query_cache.rb:64:in `call' 
activerecord (3.2.3) lib/active_record/connection_adapters/abstract/connection_pool.rb:467:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call' 
activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `_run__647780415925652457__call__1911592835196459847__callbacks' 
activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `__run_callback' 
activesupport (3.2.3) lib/active_support/callbacks.rb:385:in `_run_call_callbacks' 
activesupport (3.2.3) lib/active_support/callbacks.rb:81:in `run_callbacks' 
actionpack (3.2.3) lib/action_dispatch/middleware/callbacks.rb:27:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/reloader.rb:65:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/remote_ip.rb:31:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call' 
railties (3.2.3) lib/rails/rack/logger.rb:26:in `call_app' 
railties (3.2.3) lib/rails/rack/logger.rb:16:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/request_id.rb:22:in `call' 
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call' 
rack (1.4.1) lib/rack/runtime.rb:17:in `call' 
activesupport (3.2.3) lib/active_support/cache/strategy/local_cache.rb:72:in `call' 
rack (1.4.1) lib/rack/lock.rb:15:in `call' 
actionpack (3.2.3) lib/action_dispatch/middleware/static.rb:62:in `call' 
railties (3.2.3) lib/rails/engine.rb:479:in `call' 
railties (3.2.3) lib/rails/application.rb:220:in `call' 
rack (1.4.1) lib/rack/content_length.rb:14:in `call' 
railties (3.2.3) lib/rails/rack/log_tailer.rb:14:in `call' 
rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run' 
/Users/aziz/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread' 

有誰知道爲什麼我我得到這個錯誤嗎？

Answer 1

發生這種情況是因爲系統試圖將nil轉換爲可存儲在YAML中的值並且失敗。

看着你的代碼，我期望這是因爲你將一個零對象傳遞給傳遞給Waveform.new的變量（其操作被延遲的方法）。傳遞給new的變量將需要存儲，直到延遲的作業準備好運行該進程，並且我希望它們存儲爲YAML。

你可以重構波形要麼使第二屬性可選的（因此其價值沒有被保存）

::Waveform.new("./public" + @mix.sound_file.to_s).delay.generate(waveform, options) 

或用別的東西的含義相同爲零。例如，傳入符號：無。然後該行變爲：

::Waveform.new("./public" + @mix.sound_file.to_s, :none).delay.generate(waveform, options)