Women in Technology

I tried to resolve this problem for several hours but still didn't get the right result.
i tried to change 'recipe.category.name' to 'recipe.category_id', and it shows only a number in Category column of Recipe list.

NoMethodError in Recipe#list

Showing app/views/recipe/list.rhtml where line #13 raised:

undefined method `category' for #<Recipe:0x56b69bc>

Extracted source (around line #13):

10: <td><%= link_to %Q{#{recipe.title}}, :action => 'show', :id => recipe %>
11: <%= link_to '(delete)', {:action => 'destroy', :id => recipe },
12: :confirm => 'Are you sure?', :post => true %></td>
13: <td><%= link_to %Q{#{recipe.category.name}},
14: {:action => 'list', :category_id => recipe.category.id} %></td>
15: <td><%=h recipe.date %></td>
16: </tr>

thanks alot!