Using django-mongoengine-filter¶
django-mongoengine-filter provides a simple way to filter down a queryset based on
parameters a user provides. Say we have a Product
model and we want to let
our users filter which products they see on a list page.
The model¶
Let’s start with our model:
from django.db import models
class Product(models.Model):
name = models.CharField(max_length=255)
price = models.DecimalField()
description = models.TextField()
release_date = models.DateField()
manufacturer = models.ForeignKey(Manufacturer)
The filter¶
We have a number of fields and we want to let our users filter based on the
price or the release_date. We create a FilterSet
for this:
import django_mongoengine_filter
class ProductFilter(django_mongoengine_filter.FilterSet):
class Meta:
model = Product
fields = ['price', 'release_date']
As you can see this uses a very similar API to Django’s ModelForm
. Just
like with a ModelForm
we can also override filters, or add new ones using a
declarative syntax:
import django_filters
class ProductFilter(django_mongoengine_filter.FilterSet):
price = django_filters.NumberFilter(lookup_type='lt')
class Meta:
model = Product
fields = ['price', 'release_date']
Filters take a lookup_type
argument which specifies what lookup type to
use with Django’s ORM. So here when a user entered a price it would show all
Products with a price less than that.
It’s quite common to forget to set lookup type for `CharField`s/`TextField`s and wonder why search for “foo” doesn’t return result for “foobar”. It’s because default lookup type is exact text, but you probably want `icontains` lookup field.
Items in the fields
sequence in the Meta
class may include
“relationship paths” using Django’s __
syntax to filter on fields on a
related model:
class ProductFilter(django_mongoengine_filter.FilterSet):
class Meta:
model = Product
fields = ['manufacturer__country']
Filters also take any arbitrary keyword arguments which get passed onto the
django.forms.Field
initializer. These extra keyword arguments get stored
in Filter.extra
, so it’s possible to override the initializer of a
FilterSet
to add extra ones:
class ProductFilter(django_mongoengine_filter.FilterSet):
class Meta:
model = Product
fields = ['manufacturer']
def __init__(self, *args, **kwargs):
super(ProductFilter, self).__init__(*args, **kwargs)
self.filters['manufacturer'].extra.update(
{'empty_label': 'All Manufacturers'})
Like django.contrib.admin.ModelAdmin
does it is possible to override
default filters for all the models fields of the same kind using
filter_overrides
:
class ProductFilter(django_mongoengine_filter.FilterSet):
filter_overrides = {
models.CharField: {
'filter_class': django_filters.CharFilter,
'extra': lambda f: {
'lookup_type': 'icontains',
}
}
}
class Meta:
model = Product
fields = ['name']
The view¶
Now we need to write a view:
def product_list(request):
f = ProductFilter(request.GET, queryset=Product.objects)
return render_to_response('my_app/template.html', {'filter': f})
If a queryset argument isn’t provided then all the items in the default manager of the model will be used.
The URL conf¶
We need a URL pattern to call the view:
re_path(r'^list$', views.product_list)
The template¶
And lastly we need a template:
{% extends "base.html" %}
{% block content %}
<form action="" method="get">
{{ filter.form.as_p }}
<input type="submit" />
</form>
{% for obj in filter %}
{{ obj.name }} - ${{ obj.price }}<br />
{% endfor %}
{% endblock %}
And that’s all there is to it! The form
attribute contains a normal
Django form, and when we iterate over the FilterSet
we get the objects in
the resulting queryset.
Other Meta options¶
Ordering using order_by
¶
You can allow the user to control ordering by providing the
order_by
argument in the Filter’s Meta class. order_by
can be either a
list
or tuple
of field names, in which case those are the options, or
it can be a bool
which, if True, indicates that all fields that
the user can filter on can also be sorted on. An example or ordering using a list:
import django_filters
class ProductFilter(django_filters.FilterSet):
price = django_filters.NumberFilter(lookup_type='lt')
class Meta:
model = Product
fields = ['price', 'release_date']
order_by = ['price']
If you want to control the display of items in order_by
, you can set it to
a list or tuple of 2-tuples in the format (field_name, display_name)
.
This lets you override the displayed names for your ordering fields:
order_by = (
('name', 'Company Name'),
('average_rating', 'Stars'),
)
Note that the default query parameter name used for ordering is o
. You
can override this by setting an order_by_field
attribute on the
FilterSet
class to the string value you would like to use.
Custom Forms using form
¶
The inner Meta
class also takes an optional form
argument. This is a
form class from which FilterSet.form
will subclass. This works similar to
the form
option on a ModelAdmin.
Non-Meta options¶
Note that these options do not go in the Meta class, they are specified directly in your FilterSet class.
strict
¶
The strict
option controls whether results are returned when an invalid
value is specified by the user for any filter field. By default, strict
is
set to True
meaning that an empty queryset is returned if any field contains
an invalid value. You can loosen this behavior by setting strict
to
False
which will effectively ignore a filter field if its value is invalid.
Overriding FilterSet
methods¶
get_ordering_field()
¶
If you want to use a custom widget, or in any other way override the ordering
field you can override the get_ordering_field()
method on a FilterSet
.
This method just needs to return a Form Field.
Ordering on multiple fields, or other complex orderings can be achieved by
overriding the Filterset.get_order_by()
method. This is passed the selected
order_by
value, and is expected to return an iterable of values to pass to
QuerySet.order_by
. For example, to sort a User
table by last name, then
first name:
class UserFilter(django_filters.FilterSet):
class Meta:
order_by = (
('username', 'Username'),
('last_name', 'Last Name')
)
def get_order_by(self, order_value):
if order_value == 'last_name':
return ['last_name', 'first_name']
return super(UserFilter, self).get_order_by(order_value)
Generic View¶
In addition to the above usage there is also a class-based generic view
included in django-filter, which lives at django_filters.views.FilterView
.
You must provide either a model
or filterset_class
argument, similar to
ListView
in Django itself:
# urls.py
from django.urls import re_path
from django_filters.views import FilterView
from myapp.models import Product
urlpatterns = [
re_path(r'^list/$', FilterView.as_view(model=Product)),
]
You must provide a template at <app>/<model>_filter.html
which gets the
context parameter filter
. Additionally, the context will contain
object_list
which holds the filtered queryset.
A legacy functional generic view is still included in django-filter, although
its use is deprecated. It can be found at
django_filters.views.object_filter
. You must provide the same arguments
to it as the class based view:
# urls.py
from django.urls import re_path
from myapp.models import Product
urlpatterns = [
re_path(r'^list/$', 'django_filters.views.object_filter', {'model': Product}),
]
The needed template and its context variables will also be the same as the class-based view above.