widget.html.erb

<table>
    <thead>
        <th>Foo</th>
        <% if feature_enabled?(:premium) %>
            <th>Premium</th>
        <% end %>
    </thead>
    <tbody>
        <tr>
            <td><%= @widget.foo %></td>
            <% if feature_enabled?(:premium) %>
                <td><%= @widget.premium %></td>
            <% end %>
        </tr>
    </tbody>
</table>

widget_controller.rb

class WidgetController
    def show
        add_feature(:premium)
        @widget = Widget.find(widget_params)
    end
end