Develop Reference

Stuck with django form validation

I'm trying to get validation running on a django form used to retrieve a list of objects in a ListView View. Despite having read django docs and many other questions here, I can't find out what's wrong in this simple test code:
form.html
<form action="list.html" method="get">
{{ form }}
<input type="submit" value="Submit">
</form>
list.html
<ul>
{% for area in object_list %}
<li>{{ area.name }}</li>
{% endfor %}
</ul>
forms.py
from django import forms
class SearchArea(forms.Form):
area = forms.CharField(label='Area code', max_length=6)
def clean_area(self):
area = self.cleaned_data['area'].upper()
if '2' in area:
raise forms.ValidationError("Error!")
return area
views.py
class HomePageView(FormView):
template_name = 'form.html'
form_class = SearchArea
class AreaListView(ListView):
template_name = 'list.html'
model = AreaCentral
def get_queryset(self):
q = self.request.GET.get('area')
return AreaCentral.objects.filter(area__istartswith=q)
When I try to submit something like "2e" I would expect a validation error, instead the form is submitted. Moreover I can see in the GET parameters that 'area' is not even converted to uppercase ('2E' instead of '2e').

The default a FormView will only process the form on POST; the GET is for initially displaying the empty form. So you need to use method="post" in your template form element.
Your action attribute is also suspect; it needs to point to the URL of the form view. If that actually is the URL, note it's not usual to use extensions like ".html" in Django URLs, and I would recommend not doing so.

Django - proper way to implement threaded comments

I'm developing a blog site using Django. My site will allow users to comment on any of my blog posts and also reply to each other and will be displayed using a 'threaded comments' structure (I haven't started user functionality yet, just comments). I've got the threaded comments to work properly using django-mptt (at least, for now), but I have NO CLUE if the route or steps I'm taking are in the right direction. Almost all the tutorials I've gone through only scratch the surface when it comes to comments and doesn't talk about threaded comments in django. I want some experienced/professional advice on what I might be doing wrong and what I could be doing better. The last thing I want is to find out there was a much more acceptable way of going about, after hours of work put in.
So, here is a list of what I need clarity on:
django-mptt:
I chose this because I can afford slower write times. My site will have more reads than writes. Is this option okay for my case? Is there a better alternative I don't know about?
What should I do if my site does end up having lots of commenting activity? What could I do to optimize tree restructuring? Or would I be better off switching to an adjacency list?
My MPTT comment model has a ForeignKey referenced to itself (for replies). Is this the right way? Or should I create a separate reply model?
The way I insert a reply to another user's comment in the tree is using a hidden input within the form that's within the mptt recursive template tags, and return the input value (which is the id of the comment that the reply is for) and set the parent of the reply to that input value. Is this an accepted method?
Multiple forms on one HTML page
I have two forms on my blog post HTML page. One to comment on the blog post, and one to reply to a user's comment. Is this accepted? Or should I create different URLs and view functions for different forms? I did it this way because I wanted a Reddit style commenting system. I don't want it to have to go to a different page to comment or reply.
If a user comments on my blog post, the hidden input value within the reply form returns nothing, therefore I get an error when trying to assign it to a variable in the views.py function. I used a try/except block to fix it. Is there a better way around this?
I'm sorry if these are noob questions and for my post being so long. I just want to do things the best way possible using realistic solutions for a beginner. Any feedback would help. Thank you! Here's my code for my blog app.
models.py
from django.db import models
from mptt.models import MPTTModel, TreeForeignKey
class Post(models.Model):
"""Blog post"""
title = models.CharField(max_length=200)
body = models.TextField()
date_added = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.body[:50] + '...'
class Comment(MPTTModel):
"""User comment"""
post = models.ForeignKey(Post, related_name='comments',on_delete=models.CASCADE)
parent = TreeForeignKey('self', null=True, blank=True, related_name='children',db_index=True, on_delete=models.CASCADE)
user_comment = models.CharField(max_length=500, unique=True)
date_added = models.DateTimeField(auto_now_add=True)
# approved = models.BooleanField(default=False)
class MPTTMeta:
order_insertion_by = ['date_added']
def __str__(self):
return self.user_comment[:20]
'approved' is commented out because I get a 'no such column: approved' error for some weird reason.
forms.py
from django import forms
from .models import Post, Comment
class CommentForm(forms.ModelForm):
class Meta:
model = Comment
fields = ['user_comment']
views.py
from django.shortcuts import render
from django.http import HttpResponseRedirect
from django.urls import reverse
from .models import Post
from .forms import CommentForm
def posts(request):
"""Show all blog posts"""
posts = Post.objects.order_by('-date_added')
context = {
'posts': posts
}
return render(request, 'posts/posts.html', context)
def post(request, post_id):
"""Show single blog post"""
post = Post.objects.get(id=post_id)
comments = post.comments.all()
if request.method != 'POST':
comment_form = CommentForm()
else:
comment_form = CommentForm(data=request.POST)
try:
parent_id = request.POST['comment_id']
except:
pass
if comment_form.is_valid():
comment = comment_form.save(commit=False)
comment.post = post
comment.parent = comments.get(id=parent_id)
comment.save()
return HttpResponseRedirect(reverse('posts:post', args=[post_id]))
context = {
'post': post,
'comment_form': comment_form,
'comments': comments,
}
return render(request, 'posts/post.html', context)
post.html
{% extends 'posts/base.html' %}
{% block blog_content %}
<h1>Post page!</h1>
<h3>{{ post.title }}</h3>
<h4>{{ post.date_added }}</h4>
<p>{{ post.body }}</p>
<form method="post" action="{% url 'posts:post' post.id %}">
{% csrf_token %}
{{ comment_form.as_p }}
<button type="submit">Add comment</button>
</form>
{% load mptt_tags %}
{% recursetree comments %}
<h5>{{ node.date_added }}</h5>
<p>{{ node.user_comment }}</p>
<form method="post" action="{% url 'posts:post' post.id %}">
{% csrf_token %}
{{ comment_form.as_p }}
<input type="hidden" name="comment_id" value="{{ node.id }}">
<button type="submit">Reply</button>
</form>
{% if not node.is_leaf_node %}
<div style="padding-left: 20px">
{{ children }}
</div>
{% endif %}
{% endrecursetree %}
{% endblock %}
urls.py
from django.urls import path
from . import views
app_name = 'posts'
urlpatterns = [
path('posts/', views.posts, name='posts'),
path('posts/<int:post_id>/', views.post, name='post'),
]

MPTT trees are great for getting a list of subnodes or node counts. They are costly for adding/inserting nodes and the cost increases linearly with the size of the three. They are designed to fit tree data into relational databases. Also, don't get fooled by "I'll have much more reads than writes". Ideally, most of the reads should hit a cache, not the database under it.
Why not skip the relational database and go with a NoSQL database that can natively store trees? There are easy integrations for Django and pretty much every NoSQL database you can thing about.

In django, how generic view works

I have started learning django, I'm not sure how generic view works. I read django documentation several times, I can't gain clear understanding of how generic view works. Very strange but it works well. It retrieves data from the database and renders data on the browser.
Here is snippet code of polls/urls.py.
url(r'^$', views.IndexView.as_view(), name = 'index')
It will go to the IndexView class in views.py.
Here is snippet code of polls/views.py.
from django.views import generic
from .models import Question, Choice
class IndexView(generic.ListView):
template_name = 'polls/index.html'
context_object_name = 'latest_question_list'
def get_queryset(self):
return Question.objects.order_by('-pub_date')[:5]
When I change template_name as something, the exception has occurred as follows.
TemplateDoesNotExist: polls/question_list.html
What does question_list.html mean?
Where does it come from?
And here is index.html.
{% if latest_question_list %}
<ul>
{% for question in latest_question_list %}
<li>
{{ question.question_text }}
</li>
{% endfor %}
</ul>
{% else %}
<p>No polls are available.</p>
{% endif %}
As you can see, index.html file use latest_question_list as a parameter but I'm not sure how can the latest_question_list be used.
In views.py file, what does context_object_name = 'latest_question_list' mean?
Where does the 'latest_question_list' come from and how can index.html use latest_question_list?
Do I use context_object_name in views.py?
What's the role of the get_queryset() function?

What does question_list.html mean?
It means that there is a file inside polls dir like index.html
if you want to have a file with a diff name you have to change the name of template_name='polls/name_of_file_inside_polls'
Do I use context_object_name in views.py?
The context is the place where you put some vars to use it in your templates, that's why you can use latest_question_list
What's the role of the get_queryset() function?
It creates the query that is passed to the template.

I understand what they mean.
By default, the DetailView generic view uses a template called /_detail.html. In my case, it would use the template "polls/question_detail.html". The template_name attribute is used to tell Django to use a specific template name instead of the autogenerated default template name. I also specify the template_name for the results list view – this ensures that the results view and the detail view have a different appearance when rendered, even though they’re both a DetailView behind the scenes.
For DetailView the question variable is provided automatically – since we’re using a Django model (Question), Django is able to determine an appropriate name for the context variable. However, for ListView, the automatically generated context variable is question_list. To override this we provide the context_object_name attribute, specifying that we want to use latest_question_list instead.

Detail template in Django not taking values

from django.views import generic
from .models import Inspectionfile
from .models import posts
class IndexView(generic.ListView):
template_name = "posts/index.html"
def get_queryset(self):
return Inspectionfile.objects.all()
class DetailView(generic.DetailView):
model = Inspectionfile
template_name = "posts/detail.html "
#index template
<ul>
{% for o in object_list %}
<li>{{o.document_title}} </li>
{% endfor %}
</ul>
#detail template
<h1>{{ o.document_title }}</h1>
My Index template works but the detail template does not seem to take the value so just appears blank . So is the 'o' not being passed to detail ?? I have not been able to solve this. BTW document_title is one of the field of my inspectionfile model. I checked my url regex and it seems to work fine.

o is an object which only exists within the for loop in your list view template. It isn't passed anywhere.
The detail view has its own context; there the object that is identifued by the url argument is called just object.

Django's get_context_data function not working?

I'm practicing with Django's Class Based View.
It seems like my overridden get_context_data function is not working properly, but I have no idea what is wrong :(
My code:
urls.py
url(r'^user/(?P<pk>\d+)/posts/$', UserPosts.as_view(), name='user_post'),
views.py
class UserPosts(ListView):
template_name = 'app_blog/user_posts_page.html'
context_object_name = 'post_list'
def get_queryset(self):
self.user = get_object_or_404(User, id=self.kwargs['pk'])
return self.user.post_set.order_by('-id')
def get_context_data(self, **kwargs):
context = super(UserPosts, self).get_context_data(**kwargs)
context['user'] = self.user
return context
user_post_page.html
{% block content %}
<div class="main_content">
<h2>Welcome to {{user.username}}'s User Post Page!</he>
<ul>
{% for post in post_list %}
<li>{{post.post_title}}</li>
{% endfor %}
</ul>
</div>
{% endblock %}
The html page correctly displays the user's post_list, BUT the h2 tag displays:
Welcome to 's User Post Page!
I'm pretty sure I passed the 'user' variable in the get_context_data function, but the html page does not displa the user.username... Any idea why this is happening :(??
Thanks

Use another name that is not user. It seems like RequestContext overwrite user variable.

Please see the default TEMPLATE_CONTEXT_PROCESSORS, which set the django.contrib.auth.context_processors.auth.
If TEMPLATE_CONTEXT_PROCESSORS contains this processor, every RequestContext will contain these variables:
user – An auth.User instance representing the currently logged-in user (or an AnonymousUser instance, if the client isn’t logged in).
perms – An instance of django.contrib.auth.context_processors.PermWrapper, representing the permissions that the currently logged-in user has.
So you'd better give your user variable another name.

As the other answers said, don't use the variable name user. But even more importantly, in this particular case the ListView is not the best generic class to use; instead, you're better off using the DetailView, which makes your view much simpler:
class UserPosts(DetailView):
model = User
template_name = 'app_blog/user_posts_page.html'
context_object_name = 'listed_user'
The only change in your template is to use listed_user instead of the user variable. Since DetailView already looks into the pk URL argument, it will select and return the right User automatically.