Question

Ive been staring at this for a good day now and i dont understand what ive done wrong.
i want this to produce a list of activities with checkboxes, but if one of the activities is in the users_activity table then that that activities check box will be checked. However the code below displays the activity three times and chekcs all the boxes.

<fieldset>
    <table>
        <tr>
            <th>Activity ID</th>
            <th>Activity Name</th>
        </tr>
        <% @Activitys.each do |activity| %>
            <% @users_activity.each do |ua| %>
                <% if activity.id == ua.activity_id %>
                <tr>
                    <td><%= activity.id %></td>
                    <td><%= activity.activity_name%></td>
                    <td><input name="check_<%= activity.id %>" type="checkbox" checked="yes"></td>
                </tr>
                <% else %>
                <tr>
                    <td><%= activity.id %></td>
                    <td><%= activity.activity_name%></td>
                    <td><input name="check_<%= activity.id %>" type="checkbox" checked="no"></td>
                </tr>
                <% end %>
            <% end %>
        <% end %>
    </table>
</fieldset>

Its probably really easy but you know what happens when you stare at a piece of code for too long…

Answer 1

The reason all the checkboxes are checked is that the presence of the checked attribute on an HTML checkbox causes it to be checked regardless of the attribute’s value. i.e. <input type="checkbox" checked="no"> results in a checked checkbox. For the checkboxes that should not be checked you need to write the code such that they do not have a checked attribute at all.

The reason that you are seeing more checkboxes than you expect is because you have the @users_activity.each loop nested inside your @Activitys.each loop and in both the if and the else case you always output a checkbox so this results in @Activitys.length * @users_activity.length checkboxes.

One solution is to collect the activity IDs of all the user activities once outside your loops i.e.

<% user_activity_ids = @users_activity.collect { |ua| ua.activity_id } %>

(you could also move this to the controller)

Then have just the @Activitys.each loop in which you generate the checkbox with something like

<input name="check_<%= activity.id %>" type="checkbox"
    <%=' checked="yes"' if user_activity_ids.include? activity.id %>>

---

Also, @Activitys should probably be called @activities as starting the variable name with a capital letter indicates that it is a constant in Ruby.