Rails 3: Ruby variables in view are in NilClass

Question

Please pardon the newbie question, but I'm stumped. I'm a teacher converting a Rails
1 app to Rails 3. My "verify" controller is getting correct values from my database,
but when the view attempts to access the variables I'm told they are in "nilClass".
Here's my controller:

file ROOT/app/controllers/verify_controller.rb:

class VerifyController < ApplicationController
    @student = Assignment.get_student
    @assignments = Assignment.get_assignments
    logger.info("VERIFY: @student is #{@student}")
    logger.info("VERIFY: @assignments is #{@assignments}")
end

Here is my view:

file ROOT/app/views/verify/list.html.erb:

<?xml version="1.0" encoding="UTF-8" ?>
<!--
    This is our listing view.
-->

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
  <title>Student assignments</title>
</head>
<body>

<div id="assignment-list">

  <!-- @student is a Ruby variable.  The @ means it is a "member"
       which is accessible beyond the code that calculates it.  (The
       class is the VerifyController class, which we will be seeing
       shortly.)  See below for the angle brackets!
  -->

  <h2>Assignments for <%= @student %></h2>
  <table cellspacing="5" cellpadding="5" border="2">
    <tr>
      <th>Student</th>
      <th>Description</th>
      <th>Date received</th>
    </tr>

  <!-- HTML alone doesn't know how many rows are in the table, so
       Ruby has to look at the variables and provide a loop to do
       the rows .
  -->

  <!--  < % and % > delimit Ruby code in HTML so long as the Ruby
        doesn't produce a value (there is no blank space between
        the angle brackets and the % signs; I had to put one in
        to prevent Ruby from trying to interpret this comment!)
        If the expression does produce a value, < % = and % > are the
        delimiters.
  -->
  <% logger.info("LIST: The class of @student is #{@student.class}") %>
  <% logger.info("LIST: The class of @assignments is #{@assignments.class}") %>
  <% logger.info("LIST: @student is #{@assignments}") %>
  <% logger.info("LIST: @assignments is #{@assignments}") %>
  <% for assign in @assignments %>
     <tr>
       <td><%= assign.student %></td>
       <td><%= assign.description %></td>
       <td><%= assign.whendone %></td>
     </tr>
  <% end  # end the "for" %>
  </table>
</body>
</html>

Any suggestions?

Answer 1

You are using the variables correctly, but the error would suggest that Assignment.get_student is returning nil instead of a student. Check this method in the Assigment model.

Also, not sure if it was a paster error, but your controller should look like this:

class VerifyController < ApplicationController

  def list
    @student = Assignment.get_student
    @assignments = Assignment.get_assignments
    logger.info("VERIFY: @student is #{@student}")
    logger.info("VERIFY: @assignments is #{@assignments}")
  end

end

Rails 3: Ruby variables in view are in NilClass

Question

1 answers

solution1
0 ACCPTED 2011-04-02 17:36:50

Rails 3: Ruby variables in view are in NilClass

Question

1 answers

solution1 0 ACCPTED 2011-04-02 17:36:50

solution1
0 ACCPTED 2011-04-02 17:36:50