How can I display the number of related entries?

Question

I have a template which displays a table of all the bookings on the website. The booking channel entries consist of two fields: a related user, and a related event, 1:1. There's a drop-down list of all the events at the top of the template which lists all of the events on the site. When a user clicks on an event title, the table updates to only show bookings related to that event (done by applying a class to all rows, and hiding every row which doesn't have the same class as the chosen event slug). The filter code looks like this:

<form class="event-filter">
    <label for="filter">Filter event: </label>
    <select id="filter" name="filter">
        {% for event in craft.entries.section('event') %}
        <option value="i{{event.id}}">{{event.title}}</option>
        {% endfor %}
    </select>
</form>

The bookings table displays all the events using something like this:

{% set bookings = craft.entries.section('booking').order('postDate desc') %}

Is there a way for my filter form to list my events, and display the number of bookings for each event? So it would say, for example:

• First event (3 bookings)
• Second event (8 bookings)

I'm sure it must be possible using relations, but I can't work out the syntax.

Answer 1

Try something like this:

<form class="event-filter">
    <label for="filter">Filter event: </label>
    <select id="filter" name="filter">
        {% for event in craft.entries.section('event') %}    
            {% set numEventBookings = craft.entries.section('booking').relatedTo(event).total() %}
            <option value="i{{event.id}}">{{event.title}} ({{numEventBookings}} bookings)</option>
        {% endfor %}
    </select>
</form>

But it'll generate one database query pr event, so it might be a bit inefficient, depending on your setup.