rails 4.2 中 ApplicationController:Class 的未定义局部变量或方法“gon”

undefined local variable or method `gon' for ApplicationController:Class in rails 4.2

我似乎无法让 gon gem 使用 rails 4.2.0。我得到 "undefined local variable or method `gon' for #" 我使用正确吗?另外,我的布局 application.html.erb.

的 header 中确实有 <%= include_gon(:init => true) %>

ApplicationController

  class ApplicationController < ActionController::Base 
     gon.current_user_rolename = current_user.role.name
  end

application.js

 if(gon.current_user_rolename == 'Admin'){
    alert('success');
  }

Application.html.erb

<!DOCTYPE html>
 <html>
 <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">  
    <%= include_gon(:init => true) %>
    <%= Gon::Base.render_data({}) %>
    <!-- Main css styles -->
     <%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true %>
    <!-- Main javascript files -->
    <%= javascript_include_tag 'application', "http://localhost:9292/faye.js", 'data-turbolinks-track' => true %>    
   <%= csrf_meta_tags %>
</head>
<body >
    <%=yield%>
</body>

将此代码放在方法中 例如:

def methodname
gon.current_user_rolename = current_user.role.name
end

如果你在方法外定义,它将不起作用

也将此行放在 application.html.erb 下方 csrf_metags 行:

 <%= csrf_meta_tags %>
<%= include_gon(:init => true) %>
    <%= Gon::Base.render_data({}) %>