Pagination and django-filter

Question

I am trying to implement a search feature with pagination. I have successfully either managed to get the search to work or the pagination to work. But I cannot figure out how to get both of them working together at the same time.

Here is the .html, by switching object_list to filter.qs in the .html, I can switch between either searching correctly or pagination correctly. Can someone help me fix the code so that I can have both working together ?

{% extends 'base.html' %}
{% load widget_tweaks %}
{% load my_tags %}

{% block head %}
    <title> Overview</title>
{% endblock %}
{% block content %}
    <form method="get">
        <div class="jumbotron">
            <h4 style="margin-top: 0">Filter</h4>
            <div class="row">
                <div class="form-group col-sm-4 col-md-3">
                    {{ filter.form.name.label_tag }}
                    {% render_field filter.form.name class="form-control" %}
                </div>
                <div class="form-group col-sm-4 col-md-3">
                    {{ filter.form.city_location.label_tag }}
                    {% render_field filter.form.city_location class="form-control" %}
                </div>
            </div>
            <button type="submit" class="btn btn-primary">
                <span class="glyphicon glyphicon-search"></span> Search
            </button>
        </div>
    </form>


<table class="table table-bordered">
    <thead>
    <tr>
        <th>Name</th>
        <th>City Location</th>
    </tr>
    </thead>
    <tbody>
    {% for object in object_list %}
        <tr>
            <td>{{ object.name }}</td>
            <td>{{ object.city_location }}</td>

        </tr>
    {% empty %}
        <tr>
            <td colspan="5">No data</td>
        </tr>
    {% endfor %}
    </tbody>
</table>
<br>
<br>


<div id="footer">
    <div class="container text-center">
        <p class="text-muted credit" style="color:#fff">
            {% if is_paginated %}
                {% if page_obj.has_previous %}
                    <a href="?{% param_replace page=1 %}">First</a>
                    {% if page_obj.previous_page_number != 1 %}
                        <a href="?{% param_replace page=page_obj.previous_page_number %}">Previous</a>
                    {% endif %}
                {% endif %}
                Page {{ page_obj.number }} of {{ paginator.num_pages }}
                {% if page_obj.has_next %}
                    {% if page_obj.next_page_number != paginator.num_pages %}
                        <a href="?{% param_replace page=page_obj.next_page_number %}">Next</a>
                    {% endif %}
                    <a href="?{% param_replace page=paginator.num_pages %}">Last</a>
                {% endif %}

                <p>Objects {{ page_obj.start_index }}—{{ page_obj.end_index }}</p>
            {% endif %}
    </div>
</div>

{% endblock %}

Here is my models

from django.db import models


# Create your models here.
class lab(models.Model):
    name = models.CharField(max_length=255)
    city_location = models.CharField(max_length=255)


    def __str__(self):
        return self.Lab_name

Here is my views.py

class labListView(LoginRequiredMixin, ListView):
    context_object_name = "Lab_folders"
    model = lab
    template_name = "researcher_view_app/Lab_overview.html"
    paginate_by = 20

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['filter'] = labOverviewFilter(self.request.GET, queryset=self.get_queryset())

        return context

Here is my filters.py

import django_filters


class labOverviewFilter(django_filters.FilterSet):
    Lab_name = django_filters.CharFilter(lookup_expr='icontains')
    Lab_city_location = django_filters.CharFilter(lookup_expr='icontains')

And the part which I have no idea about, that I do not know how to modify but works is: my tempatetag

app_name/templatetags/my_tags.py

from django import template

register = template.Library()


@register.simple_tag(takes_context=True)
def param_replace(context, **kwargs):
    """
    Return encoded URL parameters that are the same as the current
    request's parameters, only with the specified GET parameters added or changed.

    It also removes any empty parameters to keep things neat,
    so you can remove a parm by setting it to ``""``.

    For example, if you're on the page ``/things/?with_frosting=true&page=5``,
    then

    <a href="/things/?{% param_replace page=3 %}">Page 3</a>

    would expand to

    <a href="/things/?with_frosting=true&page=3">Page 3</a>

    Based on
    https://stackoverflow.com/questions/22734695/next-and-before-links-for-a-django-paginated-query/22735278#22735278
    """
    d = context['request'].GET.copy()
    for k, v in kwargs.items():
        d[k] = v
    for k in [k for k, v in d.items() if not v]:
        del d[k]
    return d.urlencode()

Answer 1

You can apply filter in get_queryset method. Like this

class labListView(ListView):
    context_object_name = "Lab_folders"
    model = lab
    template_name = "researcher_view_app/Lab_overview.html"
    paginate_by = 20

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['filter'] = labOverviewFilter(self.request.GET, queryset=self.get_queryset())
        return context

    def get_queryset(self):
        qs = super().get_queryset()
        word = labOverviewFilter(self.request.GET, queryset=qs)
        return word.qs

pagination logic works after getting queryset. So provide filtered queryset to paginator.