Question

I have a model that looks like this:

class Invite(models.Model):
    user = models.ForeignKey(User)
    event = models.ForeignKey(Event)
    roles = models.ManyToManyField(Role, blank=True, null=True)
    sent =  models.BooleanField("Invite Sent", default=False, editable=False)
    created = models.DateTimeField(auto_now_add=True)

    def __unicode__(self):
        return u"%s" % self.user

    class Meta:
        unique_together =(('user','event'),)


class Role(models.Model):
    """
    This associates a user's role to an event
    """
    event = models.ForeignKey(Event, related_name="roles")
    roletype = models.ForeignKey(RoleType)
    profiles = models.ManyToManyField(Profile, related_name="roles",
            blank=True, null=True)
    modified = models.DateTimeField(auto_now=True)
    created = models.DateTimeField(auto_now_add=True)

So whenever a new Event is created, a bunch of roles gets created along with it. In the Invite model, how can I only show the roles associated with the event I’ve selected in the change form within Django Admin instead of showing all the entries in the Role model?

Answer 1

You want to dynamically filter the choices of the roles choices, so you will need ajax to perform this task.

Here’s how you can make this work..

1: OnChange of the event send the event_id to your custom view through ajax.

2: From the Roles model filter based on the event_id you got from the ajax request and return the filtered roles by serializing into JSON.

3: Clear the existing roles and repopulate by parsing through the JSON response.

Eg:
This a jquery getJSON example

javascript:

$("#event").change(function (){         
 var event_id = $(this).val();              
    $.getJSON("/my-app/my-roles-filter-view/"+ event_id +"/",function(data){
        var roles_dd = $("#roles");
        $('#event >option').remove();
        $.each(data, function(index,value) {
        roles_dd.append($("<option />").val(value).text(value));
    });                 
})(django.jquery);

url’s:

('^/my-app/my-roles-filter-view/(?P<event_id>\d+)/$','my_view'),

views:

def my_view(request,event_id):
    qs = Role.objects.filter(event=event_id).values_list('id')
    return HttpResponse(simplejson.dumps(qs),mimetype='application/javascript')

This just an example using jquery you can use any type of ajax and achieve this.