filter queryset using values_list

Date: April 25th 2016
Last updated: April 25th 2016

I'll start by describing my django objective. I have a button in an html template labeled as "join group". I will also note that this html template has been given a list of groups collected from views.py (i.e. Group.objects.all()). When the user clicks on the "join" button, data is sent to a model containing, User and Group. I am calling this the GroupRequest model. Now... I want this button to change color and the label to say "request sent".

models.py

class GroupModerator(models.Model):
    """
    Extends the group model. This model is used to provide editable control
    over the groups privacy and accepting user requests.
    """
    group_user = models.ForeignKey(User)
    group_id = models.ForeignKey(Group)
    STATUS = (('Open', 'Open'),('Full', 'Full'),)
    group_status = models.CharField(max_length=4, choices=STATUS,default='Open')
    def __str__(self):
        return '{} --> {}'.format(self.group_user, self.group_id)

class GroupRequest(models.Model):
    """
    A model to temporarily store User requests. The GroupModerator is included
    so that they are alerted to a new request.
    """
    user_requesting_groupjoin = models.ManyToManyField(User)
    group_moderator_id = models.ForeignKey(GroupModerator)
    group_id = models.ForeignKey(Group)
    def __str__(self):
        return '{}'.format(self.user_requesting_groupjoin)

views.py
Send data to html template.

@login_required
def groups(request):
    groups_list = Group.objects.all()
    context = {'groups_list': groups_list}
    return render(request, 'surferprofile/groups.html', context)

My expectation is that I can access both GroupRequest and GroupModerator from the html template because they are connected to Group with a ForeignKey.

For example, I can do this...

<!--groups.html-->
{{group.grouprequest_set.all.0.user_requesting_groupjoin.id}}

However, this will only get the first User in the queryset. If I back up to get the queryset I seem to need to iterate over the list to access the content (i.e. for loop). That is, I can't seem to ask if a user is in this set.

<!--groups.html-->
{{group.grouprequest_set.all}}

Here is the context in which the button must change...

Groups.html

{% for group in groups_list %}
    <!-- snipped (buttons appear in table format) -->

        <!-- Warning: The following if statement is an indicator only 
        which is meant to show my logic -->
        {% if GROUP_REQUEST in GROUP %} <!-- PROBLEM LINE -->

            <!-- Note that join_group populates the GroupRequest Table -->
            <a href="{% url 'surferprofile:join_group' my_group_id=group.id %}">
            <button style="width: 120px; margin-left: 2%;"
                    type="button"
                    class="btn btn-success"> sent
            </button>
            </a>
        {% else %}

            <!-- There is programming logic in join_group function to 
            only allow one user request per group -->
            <a href="{% url 'surferprofile:join_group' my_group_id=group.id %}">
            <button style="width: 120px; margin-left: 2%;"
                    type="button"
                    class="btn btn-primary"> Join group
            </button>
            </a>
        {% endif %}
{% endfor %}

My solution was to go back to views.py and provide a filtered list to groups.html by using a values_list. This means I only need to check that the group id is found in the GroupRequest model. I.e. my filtered values_list.

views.py

@login_required
def groups(request):
    groups_list = Group.objects.all()
    group_values_list = GroupRequest.objects.filter(
                        user_requesting_groupjoin=request.user).values_list(
                        'group_id', flat=True)
    context = {'groups_list': groups_list, 'group_values_list': group_values_list}
    return render(request, 'surferprofile/groups.html', context)

groups.html (update)

{% for group in groups_list %}
    <!-- snipped -->
        {% if group.id in group_values_list %} <!-- MODIFIED LINE -->
            <a><button><!--snipped--> </button></a>
        {% else %}
            <a><button><!--snipped--> </button></a>
        {% endif %}
{% endfor %}