Although in reality, you might want to keep award listings around when students leave, for demonstration purposes it’s worth considering the problem of orphaned records. The validates_existence_of plug-in described earlier can check that a corresponding student record exists at the time the award record is created, but once the record has been created, validation doesn’t notice, for example, if the student is deleted. Keeping award records in sync with student records requires something more active.

Rails makes it very easy to make sure that when student records are deleted, the corresponding awards records are also deleted. You just need to add an option to the has_many declaration in app/models/student.rb:

has_many :awards, :dependent => :destroy

This is powerful and easy, but beware: those deletions will take place without any further confirmation. Once the user agrees to delete a student record, all of the awards records connected to that student will also disappear.

While adding the awards list to the main list of students could get really verbose, it does make sense to add a count of awards received to the list of students. If you add the set of awards listed in Figure B-3 of Appendix B, you’ll have an awards list like that shown in Figure 9-5.

Adding a count of these awards to the students list that’s in app/views/students/index.html.erb is simple. There needs to be a new column for awards, so at the end of the first row (in the first tr element), add:

<th>Awards</th>

Figure 9-5. A brief students list

And then, after:

<td><%=h student.start_date %></td>

add:

<td><%=h student.awards.count %></td>

Just as every award object now has a student object because of belongs_to, every student object has an awards object, thanks to the has_many declaration. Getting a count of awards for that student is as simple as specifying count. Figure 9-6 shows the results of these additions.

Figure 9-6. A students list complete with count of awards

You’ll probably want to format them more beautifully, but the basic data is there. It also makes sense to add a list of awards to each of the individual student views, so that users can see what students have won as they review the records. Thanks to the awards method, it isn’t difficult to add an awards table to app/views/students/show.html.erb:

<h3>Awards</h3>
<table>
  <tr>
    <th>Name</th>
    <th>Year</th>
    <th>Student</th>
  </tr>

<% for award in @student.awards %>
  <tr>
    <td><%=h award.name %></td>
    <td><%=h award.year %></td>
    <td><%=h award.student.name %></td>
  </tr>
<% end %>
</table>

In the view, the @student variable contains the current student. Running a for loop over the collection returned by @student.awards, which contains only the awards for the current student, lets you put the information about the awards into a table. You’ll get a result like that shown in Figure 9-7.

Figure 9-7. A student record with awards listed