Queried Results from Database Disappear on Pagination: Django - django

Question

I am new to using the Django framework. I am creating a form to take in User input to query a database. I want to display the queried results on the same page, below the from fields. I am able to do the same. However, upon implementing Pagination, and clicking the 'next' link, or trying to sort the results using 'order_by', the queried results disappear from the webpage. How can this be resolved?
Below are my code files:\
views.py:
def get(self, request, *args, **kwargs):
paginated_objects = []
order_by = None
form = QueryForm(request.GET)
button_state = True
if form.is_valid():
max_traj_len = form.data["traj_len_user"]
print(form.data["submit"])
print(max_traj_len)
order_by = request.GET.get('order_by', 'traj_len') ##default order_by is set here
backtrack_flag = form.data["backtrack_user"]
print(backtrack_flag)
queried_objects = list(collection.find({'traj_len':{'$lte':int(max_traj_len)}}))
paginator = Paginator(queried_objects, 25)
page = request.GET.get('page')
paginated_objects = paginator.get_page(page)
button_state = request.GET.get('submit')
return render(request, self.template_name, {'form': form,'object_list': paginated_objects, 'order_by': order_by, 'button_state': button_state})
template.html:
{% extends 'base.html' %}
{% block content %}
<form action='' method='get'>
{% csrf_token %}
<table>{{ form.as_table }}</table>
<input type="submit" name="submit" value="Query">
</form>
{% if button_state == 'Query' %}
<table id="studata">
<thead>
<th>Traj ID</th>
<th>Traj Path</th>
<th>Traj Length</th>
<th>Interpolated_ID</th>
<th>Interpolated Path</th>
<th>Interpolated Path Length</th>
<th>Backtrack</th>
<th>Reached Goal</th>
</thead>
{% for obj in object_list %}<tr>
<script type="text/javascript">
var ele = {{ obj.traj_path }};
var last_ele = ele.pop()
//assuming 0 is the goal trajectory: change if another json is the goal state
if(last_ele == 0){
goal = "True"
}
else{
goal = "False"
}
</script>
<td><a href = '/hoc4/{{ obj.traj_id }}' >{{ obj.traj_id }}</a></td>
<td>{{ obj.traj_path }}</td>
<td>{{ obj.traj_len }}</td>
<td>{{ obj.interpolated_id }}</td>
<td>{{ obj.inter_path }}</td>
<td>{{ obj.inter_path_len }}</td>
<td>{{ obj.backtrack }}</td>
<td><script type="text/javascript">
document.write(goal)
</script>
</td>
</tr>
{% endfor %}
</table>
<div class="pagination">
<span class="step-links">
{% if object_list.has_previous %}
« first
previous
{% endif %}
<span class="current">
Page {{ object_list.number }} of {{ object_list.paginator.num_pages }}.
</span>
{% if object_list.has_next %}
next
last »
{% endif %}
</span>
</div>
{% endif %}
{% endblock %}
forms.py:
class QueryForm(forms.Form):
traj_len_user = forms.IntegerField(min_value=0, required=True)
backtrack_user = forms.BooleanField()

Answer 1

You're doing a lot of extra stuff that seems like you don't even need... You don't need a form for querying anything. You only need whatever's in request.GET and request.POST. You can access them by request.GET.get('name_attribute_of_input'), and so on.
Here's the relevant portion of how to use a Paginator class.
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
def get_something(request):
object_list = MyModel.published.all()
tag = None
paginator = Paginator(object_list, 3) # 3 objects on each page
page = request.GET.get('page') # this is getting the 'page' quesry string argument in the url as a GET request, so ?page=whatever_url
try:
my_models = paginator.page(page) # by itself without paginator, object_list would get all my_models and put it on one page. But the paginator object here converts the X objects into pages.
# And those pages are reached by the page variable above that GET's it.
except PageNotAnInteger:
# If page is not an integer, deliver the 1st page
my_models = paginator.page(1)
except EmptyPage:
# If page is out of range deliver last page of results
my_models = paginator.page(paginator.num_pages)
return render(request, 'blog_app/list.html', {'page': page, 'my_models': my_models})
And your template would have something like this in it:
{% if page.has_previous %}
Previous
{% endif %}
<span class="current">
Page {{ page.number }} of {{ page.paginator.num_pages }}.
</span>
{% if page.has_next %}
Next
{% endif %}