未定義的方法`每個'做主題

我收到以下未定義的方法each錯誤。我跟着Lynda上的練習一起跟着我被卡在這裏。我試圖理解其他問題中的解決方案，但仍然超出我的理解範圍。任何幫助將不勝感激。未定義的方法`每個'做主題

ActionView::Template::Error (undefined method `each' for nil:NilClass): 
    10:    <th>Pages</th> 
    11:    <th>Actions</th> 
    12:   </tr> 
    13:   <% @Subjects.each do|subject| %> 
    14:   <tr> 
    15:    <td><%= subject.position %></td> 
    16:    <td><%= subject.name %></td> 
    app/views/subjects/index.html.erb:13:in `_app_views_subjects_index_html_erb__3548269486732453408_70351994996820'

這裏是在models/views/subjects/index.html.erb

<div class = "subjects index"> 
    <h2>Subjects</h2> 
    <%= link_to("Add New Subject",'#', :class => 'action new') %> 

    <table class ="listing" summary ="Subject list"> 
    <tr class = "header"> 
     <th>&nbsp;</th> 
     <th>Subject</th> 
     <th>Visible</th> 
     <th>Pages</th> 
     <th>Actions</th> 
    </tr> 
    <% @Subjects.each do|subject| %> 
     <tr> 
     <td><%= subject.position %></td> 
     <td><%= subject.name %></td> 
     <td class ="center"><%= subject.visible ? 'Yes' : 'No' %></td> 
     <td class = "center"><%= subject.pages.size %></td> 
     <td class = "action"> 
      <%= link_to("Show", '#',:class => 'action show') %> 
      <%= link_to("Edit", '#' ,:class => 'action edit') %> 
      <%= link_to("Delete", '#',:class => 'action delete') %> 
     </td> 
     </tr> 
    <% end %> 
    </table> 
</div>

主題模型中定義爲如下的索引代碼：

class Subject < ActiveRecord::Base 
    has_many :pages 

    scope :visible, lambda { where(:visible => true) } 
    scope :invisible, lambda { where(:visible => false) } 
    scope :sorted, lambda { order("subjects.position ASC") } 
    scope :newest_first, lambda { order("subjects.created_at DESC")} 
    scope :search, lambda {|query| 
    where(["name LIKE ?", "%#{query}%"]) 
    } 

end

當i型Subject.all

irb(main):001:0> Subject.all 
    Subject Load (0.2ms) SELECT `subjects`.* FROM `subjects` 
=> #<ActiveRecord::Relation [#<Subject id: 1, name: "Initial Subject", position: 1, visible: true, created_at: "2015-04-28 04:11:54", updated_at: "2015-04-28 04:18:58">, #<Subject id: 2, name: "Revised Subject", position: 2, visible: true, created_at: "2015-04-28 04:15:01", updated_at: "2015-04-28 04:22:12">, #<Subject id: 4, name: "Third Subject", position: 3, visible: false, created_at: "2015-04-28 04:31:04", updated_at: "2015-04-28 04:31:04">]>

來源

2015-04-30 michael fouad

您的實例變量'@ Subjects'是大寫字母。這將是'@科目'。 – Emu

也添加控制器代碼。 –

謝謝你解決了這個問題。然而，另一個出現。這次是'undefined method' name'' 還突出顯示此行 '<％= subject.pages.size％>' 如果有人能解釋爲什麼會發生這種情況，我會真的很感激它。當我使用'.count'替換'.size'時，我使用了 –