我在创建一个可以在rails中播放音乐的应用时遇到问题。我似乎无法从数据库中实际获取歌曲的属性。模型类名为“音乐”。我得到的错误是：
uninitialized constant Music::Title
尝试运行此代码时：
<div id="player">
<% @musics.each do |song| %>
<%= song.title %>
<div>Play sound #1: <a href="#" onclick="play('sound1');">play</a></div>
<% end %>
<%= initialize_sounds(sounds, debug=false) %>
音乐课的属性是
create_table "musics", :force => true do |t|
t.integer "song_id"
t.string "title"
t.string "tracklist"
t.string "info"
t.string "music_location"
t.datetime "created_at"
t.datetime "updated_at"
end
有趣的是，如果我拿出song.title，我会得到两个'play sound＃1 div'的条目。这意味着它识别出数据库中有两个条目。从模型中获取属性我做错了什么？这是通过渲染部分来查看的。我能够在应用程序中使用帖子模型做类似的事情并且工作正常。我创建了一个名为@musics的数据库查询来查找歌曲。我尝试将变量从@musics更改为@songs以防应用程序混淆但没有运气。此外，如果我使用标准脚手架来查看歌曲的索引，它们都显示正常。任何建议都将不胜感激。
--- ------更新
这是music.rb文件：
class Music < ActiveRecord::Base
has_one :title
has_one :music_location
validates_uniqueness_of :song_id
def self.save(upload)
name = upload['datafile']
directory = "public/music/"
# create the file path
path = File.join(directory, name)
#write the file
File.open(path, "wb") { |f| f.write(upload['datafile'])}
end
def self.player
find(:all, :conditions=> "select == true")
end
end
这是开发日志信息：
Started GET "/" for 127.0.0.1 at 2011-12-31 08:28:53 -0600
Processing by PagesController#_home as HTML
[1m[35mMusic Load (0.0ms)[0m SELECT "musics".* FROM "musics"
[1m[36mPost Load (0.0ms)[0m [1mSELECT "posts".* FROM "posts" [0m
Rendered posts/_news.html.erb (24.0ms)
Rendered pages/_home.html.erb within layouts/application (28.0ms)
[1m[35mCACHE (0.0ms)[0m SELECT "posts".* FROM "posts"
Rendered posts/_news.html.erb (1.0ms)
Rendered pages/_home.html.erb (2.0ms)
Rendered musics/_player.html.erb (5.0ms)
Rendered pages/_music.html.erb (11.0ms)
Completed 500 Internal Server Error in 93ms
ActionView::Template::Error (uninitialized constant Music::Title):
3: <% @musics.each do |song| %>
4:
5:
6: <%= song.title %>
7: <div>Play sound #1: <a href="#" onclick="play('sound1');">play</a></div>
8:
9:
app/views/musics/_player.html.erb:6:in `block in _app_views_musics__player_html_erb__288302969_49298280'
app/views/musics/_player.html.erb:3:in `each'
app/views/musics/_player.html.erb:3:in `_app_views_musics__player_html_erb__288302969_49298280'
app/views/pages/_music.html.erb:12:in `_app_views_pages__music_html_erb___111175075_22835100'
app/views/layouts/application.html.erb:48:in `_app_views_layouts_application_html_erb__149306977_49748748'
Rendered c:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.1/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms)
Rendered c:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.0ms)
Rendered c:/Ruby192/lib/ruby/gems/1.9.1/gems/actionpack-3.1.1/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (24.0ms)
和完整的痕迹
activerecord (3.1.1) lib/active_record/base.rb:1341:in `compute_type'
activerecord (3.1.1) lib/active_record/reflection.rb:173:in `klass'
activerecord (3.1.1) lib/active_record/associations/association.rb:118:in `klass'
activerecord (3.1.1) lib/active_record/associations/association.rb:166:in `find_target?'
activerecord (3.1.1) lib/active_record/associations/association.rb:138:in `load_target'
activerecord (3.1.1) lib/active_record/associations/association.rb:56:in `reload'
activerecord (3.1.1) lib/active_record/associations/singular_association.rb:9:in `reader'
activerecord (3.1.1) lib/active_record/associations/builder/association.rb:41:in `block in define_readers'
app/views/musics/_player.html.erb:6:in `block in _app_views_musics__player_html_erb__288302969_39714996'
app/views/musics/_player.html.erb:3:in `each'
app/views/musics/_player.html.erb:3:in `_app_views_musics__player_html_erb__288302969_39714996'
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actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:228:in `block (2 levels) in render'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:33:in `block in instrument'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument'
activesupport (3.1.1) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `instrument'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:33:in `instrument'
actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:227:in `block in render'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:22:in `wrap_formats'
actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:219:in `render'
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actionpack (3.1.1) lib/action_view/helpers/rendering_helper.rb:27:in `render'
app/views/pages/_music.html.erb:12:in `_app_views_pages__music_html_erb___111175075_22835100'
actionpack (3.1.1) lib/action_view/template.rb:144:in `block in render'
activesupport (3.1.1) lib/active_support/notifications.rb:55:in `instrument'
actionpack (3.1.1) lib/action_view/template.rb:142:in `render'
actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:256:in `render_partial'
actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:228:in `block (2 levels) in render'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:33:in `block in instrument'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument'
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actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:227:in `block in render'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:22:in `wrap_formats'
actionpack (3.1.1) lib/action_view/renderer/partial_renderer.rb:219:in `render'
actionpack (3.1.1) lib/action_view/renderer/renderer.rb:41:in `render_partial'
actionpack (3.1.1) lib/action_view/helpers/rendering_helper.rb:27:in `render'
app/views/layouts/application.html.erb:48:in `_app_views_layouts_application_html_erb__149306977_49748748'
actionpack (3.1.1) lib/action_view/template.rb:144:in `block in render'
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actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:12:in `block in render'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:22:in `wrap_formats'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:9:in `render'
actionpack (3.1.1) lib/action_view/renderer/renderer.rb:36:in `render_template'
actionpack (3.1.1) lib/action_view/renderer/renderer.rb:17:in `render'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:120:in `_render_template'
actionpack (3.1.1) lib/action_controller/metal/streaming.rb:250:in `_render_template'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:114:in `render_to_body'
actionpack (3.1.1) lib/action_controller/metal/renderers.rb:30:in `render_to_body'
actionpack (3.1.1) lib/action_controller/metal/compatibility.rb:43:in `render_to_body'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:99:in `render'
actionpack (3.1.1) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:40:in `block (2 levels) in render'
activesupport (3.1.1) lib/active_support/core_ext/benchmark.rb:5:in `block in ms'
c:/Ruby192/lib/ruby/1.9.1/benchmark.rb:310:in `realtime'
activesupport (3.1.1) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:40:in `block in render'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:78:in `cleanup_view_runtime'
activerecord (3.1.1) lib/active_record/railties/controller_runtime.rb:24:in `cleanup_view_runtime'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:39:in `render'
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actionpack (3.1.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.1.1) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
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activesupport (3.1.1) lib/active_support/callbacks.rb:425:in `_run__593797494__process_action__1048922870__callbacks'
activesupport (3.1.1) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks'
activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument'
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actionpack (3.1.1) lib/action_controller/metal/params_wrapper.rb:201:in `process_action'
activerecord (3.1.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.1.1) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.1.1) lib/action_controller/metal.rb:193:in `dispatch'
actionpack (3.1.1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
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rack (1.3.5) lib/rack/etag.rb:23:in `call'
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actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
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railties (3.1.1) lib/rails/rack/content_length.rb:16:in `call'
railties (3.1.1) lib/rails/rack/log_tailer.rb:14:in `call'
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c:/Ruby192/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
c:/Ruby192/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
c:/Ruby192/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'
答案 0 :(得分：1)
从音乐模型中删除has_one :title和has_one :music_location。
你可能也应该有一个belongs_to :song。
我认为您不了解has_one的作用。当您说：has_one :title时，就意味着有一个Titles表，其中包含music_id列。
您无需在模型中执行任何操作即可编写song.title，这只是音乐模型的一个属性。