I have created a Wagtail settings page that allows me to select 1-5 pages which I'd like to display in my site footer as 'Most popular pages'. I've done this using an Orderable and PageChooserPanel, see below:
#register_setting
class MostPopularPosts(BaseSetting, ClusterableModel):
display_most_popular_posts_in_sidebar = models.BooleanField("Display most popular posts in sidebar", default=True, help_text='Untick to hide the most popular posts widget')
panels = [
FieldPanel('display_most_popular_posts_in_sidebar'),
InlinePanel('popular_pages', max_num=5, min_num=1, label="Most popular pages"),
]
class MostPopularPostPages(Orderable):
settings_page = ParentalKey(MostPopularPosts, related_name="popular_pages")
popular_page = models.ForeignKey(
'wagtailcore.Page',
null=True,
blank=True,
on_delete=models.SET_NULL,
related_name='+',
verbose_name="Page Link"
)
panels = [
PageChooserPanel('popular_page')
]
The above works fine, but I'm struggling to get the content of the individual pages selected to appear in my templates.
{% for popular_page in settings.home.MostPopularPosts.popular_pages.all %}
<li>
{{ popular_page.title }}
</li>
{% endfor %}
The above loop iterates the expected number of times, but {{ popular_page.title }} doesn't output the page titles. I've tried {{ popular_page.specific.title }} but this also doesn't work.
If someone could explain how I should be structuring my template tags to access the individual pages data within my for loop here I'd be eternally grateful.
Your loop will return instances of the MostPopularPostPages model, which are not page objects in their own right. To get a page object (and thus access the title field), you'll need to follow the ForeignKey that points to wagtailcore.Page, which is the popular_page relation. Renaming your existing popular_page variable to item to avoid confusion, we get:
{% for item in settings.home.MostPopularPosts.popular_pages.all %}
<li>
{{ item.popular_page.title }}
</li>
{% endfor %}
Related
I have a model which looks like this:
class Category(models.Model):
name = models.CharField(max_length=50)
slug = models.SlugField()
parent = models.ForeignKey(
'categories.Category',
null=True,
blank=True,
on_delete=models.CASCADE,
related_name='categories'
)
basically, in the parent field, it references itself. If a parent is set to None, it's the root category.
I use it to build a hierarchy of categories.
What would be the most efficient way to:
fetch all the objects through the hierarchy
display them in a template?
For some reason, select_related does not seem to lead to performance improvements here.
I also found this: How to recursively query in django efficiently?
But had a really hard time applying it to my example, because I still don't really understand what's going on. This was my result:
WITH RECURSIVE hierarchy(slug, parent_id) AS (
SELECT slug, parent_id
FROM categories_category
WHERE parent_id = '18000'
UNION ALL
SELECT sm.slug, sm.parent_id
FROM categories_category AS sm, hierarchy AS h
WHERE sm.parent_id = h.slug
)
SELECT * FROM hierarchy
Would appreciate any help.
Thanks!
One possible solution can be using https://django-mptt.readthedocs.io/en/latest/overview.html#what-is-django-mptt
MPTT is a technique for storing hierarchical data in a database. The
aim is to make retrieval operations very efficient.
The trade-off for this efficiency is that performing inserts and moving items around the tree is more involved, as there’s some extra work required to keep the tree structure in a good state at all times.
from django.db import models
from mptt.models import MPTTModel, TreeForeignKey
class Category(MPTTModel):
name = models.CharField(max_length=50)
slug = models.SlugField()
parent = TreeForeignKey(
'self',
null=True,
blank=True,
on_delete=models.CASCADE,
related_name='children'
)
class MPTTMeta:
order_insertion_by = ['name']
You can use the django-mptt template tag as this:
{% load mptt_tags %}
<ul>
{% recursetree categories %}
<li>
{{ node.name }}
{% if not node.is_leaf_node %}
<ul class="children">
{{ children }}
</ul>
{% endif %}
</li>
{% endrecursetree %}
</ul>
There is a tutorial and more information int library docs.
I had the same problem and ended up creating the following function that hits the database once, then sorts out the heirarchy and returns a dict:
def get_category_tree():
categories = Category.objects.order_by('name')
itemtree = {}
# Add 'children' attribute to each category; populate dict
for category in categories:
category.children = {}
itemtree[category.pk] = category
# Add categories to 'children'
for key,value in itemtree.items():
if value.parent_id:
itemtree[value.parent_id].children[key] = value
# Return top-level items
return {k:v for k,v in itemtree.items() if not v.parent_id}
Each value of the returned dict is a top-level Category object which has a children attribute.
You can render it in the template by looping through the dict values. The following example will handle three levels of heirarchy:
<ul>
{% for level1 in category_tree.values %}
<li>
{{ level1.name }}
{% if level1.children %}
<ul>
{for level2 in level1.children.values %}
<li>{{ level2.name }}
{% if level2.children %}
<ul>
{for level3 in level2.children.values %}
<li>{{ level3.name }}</li>
{% endfor %}
</ul>
{% endif %}
</li>
{% endfor %}
</ul>
{% endif %}
</li>
{% endfor %}
</ul>
If you need to render many levels of the heirarchy, you could consider using template recursion. Have a read of the following question and answers to determine if that might be suitable: Represent a tree of objects in Django template
"I made a parent class model where i put some fields which are related with many to many fields. I want to get all individual data from many to many field using the query of parent class. When i do these i get the all query set of the field.
I tried ,match = Match.objects.all() in views function..
then i tried {{ match.mega_league.pool_price }} to get the value..but its not working on template...
models:
class Match(models.Model):
mega_league = models.ManyToManyField('MegaLeague', blank=True)
class MegaLeague(models.Model):
price_pool = models.IntegerField() winner = models.IntegerField()
views:
match = Match.objects.all()
templates:
{{ match.mega_league.pool_price }}
but it's not working..
'''
when i use {{ match.mega_league.pool_price }} this give me blank result but in database i have data for price_pool and winner also... i need the individual access for price_pool and winner..."
match is a queryset, a list of all Matches. You need to loop through them. Then for each match, mega_league is also a queryset, si you need to iterate through the leagues.
<ul>
{% for m in match %}
<li><ul>
{% for league in match.mega_league.all %}
<li>{{ league.pool_price }} </li>
{% endfor %}
</ul></li>
{% endfor %}
</ul>
I have two models related by a Foreign key as follows. (Only shown important fields here.)
in model:
class Category(models.Model):
name = models.CharField(max_length=50, unique=True)
description = models.TextField()
...
class Price(models.Model):
category = models.ForeignKey(Category) # referred to above model
sub_type = models.CharField(max_length=4, choices=CHOICE_SUB_TYPE)
price = models.DecimalField()
...
I'm going to display Categories in a ListView along with related pricing details. In order do that, I need to set related pricing objects for each Category object. What is the best and efficient way to do this?
Your code is fine as it is, in templates, you have access to related models. When listing categories in your template you can:
<ul>
{% for cat in categories %}
<li>{{ cat.name }}</li>
<ul>
{% for price in cat.price_set.all %}
{{ price.price }}
{% endfor %}
</ul>
{% endfor %}
</ul>
For displaying categories when showing details for a price, you might want to Use a Single object Mixin with a ListView.
Recommended: Related object reference.
I am printing a list of beers matching some filters, and the bars where each is on tap. These are in a manytomany relationship. I need to filter this list of bars to only show those in a given state.
I can achieve this using if statements in the template, but then am unable to format the list to use commas with an 'and' before the final item (like https://stackoverflow.com/a/3649002/6180992), as I do not know the length of the list.
I have thought of three ways this might be possible, but cannot get any to work:
filtering the bars related field as well as the beers in the views
assembling the list in the template before looping through again to print it
filtering the bars related field in the template
Here are the relevant sections of code:
models.py
class Bar(models.Model):
bar = models.CharField(max_length=200, default='FinshnPig')
state = models.CharField(max_length=200,default='NY')
def __str__(self):
return self.bar
class Meta:
ordering = ('bar','region')
class Tap(models.Model):
bar = models.ManyToManyField(Bar,default='FinshnPig')
brewery = models.CharField(max_length=200)
beer = models.CharField(max_length=200)
state = models.CharField(max_length=200, default='NY')
def __str__(self):
return self.beer
views.py
f = TapFilter(request.GET, queryset=Tap.objects.filter(state="VIC"))
template:
{% for tap in filter %}
<li>
<b>{{ tap.beer }}</b>
<em>{{ tap.brewery }}</em>
#{% for bar in tap.bar.all %}{% if bar.state == "VIC" %}{{ bar.bar }}</b>{% endif %}{% include "taplists/comma.html" %}{% endfor %}
</li>
{% endfor %}
You can use prefetch for querying only the related bars before sending it to template, like so:
prefetch = Prefetch(
'bar',
queryset=Bar.objects.filter(state=CHOSEN_STATE),
to_attr='selected_states'
)
filter = Tap.objects.filter(state=CHOSEN_STATE).prefetch_related(prefetch)
Now inside your template use the custom attribute you assigned:
{% for tap in filter %}
# Now selected_bars only contains the bars in the state you want
{% for bar in tap.selected_bars.all %}
...
{% endfor %}
{% endfor %}
Additional info on Django docs for prefetch_related
Note: Using prefetch for ManyToMany relations will also increase the performance, as there won't be as many database lookups.
I need to understand a bit better how do FK/m2m relationships work.
I've prepared Images model for uploading images and it has an additional feature - it can be categorized by adding to a specific gallery (m2m relation to gallery).
To access gallery name I just had to do a query set for example:
Images.objects.filter(gallery__gallery_name = '')
I'd like to reverse the query a little bit so from Gallery model I can access pictures which are in specific gallery (gallery_name).
How I can do that?
Models:
class Images(models.Model):
image = models.ImageField(upload_to=update_filename, blank=True, null=True, verbose_name="Obrazek")
gallery = models.ForeignKey('Gallery', blank=True, null=True)
class Gallery(models.Model):
gallery_name = models.CharField(max_length=128)
gallery_description = models.TextField(blank=True, null=True)
View:
def index(request):
p = Gallery.objects.filter(gallery_name="main").order_by('-id')
return TemplateResponse(request, 'gallery.html',
{'gallery': p,
},)
Template:
{% for n in gallery.all %}
<h2 class="center">{{n.gallery_name}}</h2>
<hr>
{% for n in gallery.images_set %}
<div class="grid_4">
{{ n.image }}
</div>
{% endfor%}
Try something along the lines of:
# models.py
class Gallery(models.Model):
name = models.CharField(max_length=30)
description = models.CharField(max_length=200, null=True)
images = models.ManyToMany(Image)
class Image(models.Model):
title = models.CharField(max_length=30)
caption = models.CharField(max_length=200, null=True)
image = models.ImageField(upload_to=SOMEPLACE_FOR_MEDIA)
From here you should be able to do things like:
image = Image.objects.get(title="Girl Holding Cheese")
related_galleries = image.gallery_set.all()
or something similar as needed to pull what you want. The same goes the other way. To pull all images in a gallery you would do
gallery = Gallery.objects.get(name="Cheesy Wimmin")
related_images = gallery.images.all()
Though the assignments at the end aren't necessary, I usually just pass gallery.images.all() or image.gallery_set.all() directly. Note the "_set" at the end of the reference from the object that does not contain the M2M definition.
On the subject of direct usage, you can do compound references like
Image.objects.get(title="Girl Holding Cheese").gallery_set.all()
as well, but you have to decide when this makes code more clear and concise and when it just makes it more confusing to read later.
I hope this put you in the right direction.
Update
In your comment below you noticed that you cannot do
images = Images.objects.filter(gallery_set="Cheesy Wimmins")
related_galleries = images.gallery_set.all()
This is because you would be trying to filter() or all() on a queryset, not an individual model. So to make this work you can use a for loop in your template. Something like
# views.py
galleries = Gallery.objects.all()
return render(request, 'some/template.html', {'galleries': galleries})
And then
<!-- templates/some/template.thml -->
{% for gallery in galleries %}
<div class="gallery">
<h2>{{ gallery.name }}</h2>
{% for item in gallery.images.all %}
<div class="image">
{{ item.image }}
</div>
{% endfor %}
</div>
{% endfor %}
or something like this. Of course, you need to do whatever formatting steps you want to make this look right, but that's a way to get at your data.
The problem is with the {% for n in gallery.images_set %} bit in your template. images_set is a related manager, not a queryset. To get a queryset, you need to call all or another of the DBAPI methods that return querysets. So, just change it to gallery.images_set.all, and you're good.
gallery is a QuerySet - it doesn't have a images_set.
This is where naming your variables more appropriately can easily start preventing these problems: for example, galleries would be more appropriate for a list of Gallery objects... then, galleries.images_set would immediately raise red flags.
Anyways, you need to call images_set on what you've called n
{% for n in gallery.all %}
<h2 class="center">{{n.gallery_name}}</h2>
<hr>
{% for n in n.images_set.all %}
<div class="grid_4">
{{ n.image }}
</div>
{% endfor%}