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How can I create a submit form in Django with a dropping down list?

I am just starting to work with Django and I have some problems with forms and dropping lists.
I have a model with two attributes, and I want to display one of the attributes in a dropping down list (this one will be unchangeable) and another one in a text field (this one will be changeable). Also, I have a submit button, so I want to change a second attribute in a text field and by pressing on the button. How can I do this? What would some examples be?

As you are starting to work with Django, you might or might not know about how Django handle forms.
In Django, forms can be handled in two ways:
User-created and managed forms (without any form class)
Class-managed forms (connected to Django models)
Documentation form Django Forms
Now let’s talk about the first type of forms (where you create your HTML form and manage the request sent to server):
These forms are simple to make and when there are only a few and are only suggested when you have a very small amount of inputs (I would say four or fewer inputs).
Here is a simple example of subscription of a newsletter with an email example.
<form id='sub-form' method="POST">
{% csrf_token %}
<div>
<input type="email" name="sub_email">
</div>
<input class="button" value="Subscribe" type="submit" id="subbutton">
</form>
So a very important thing to look at here is {% csrf_token %}, about which you can read more about here and about how it works and prevents cross-site request forgery. This token will be required when you make a request to Django server with any post request and data.
In this subscription form you see one <input> with name="sub_email". Take note of this as we will use this to get this value on the server as this is the key to its value, and then a simple Submit Button.
When you press Submit on a page let’s say url = "http://BASE_URL/home" you will receive a POST request on the view that handles that URL.
So now coming to the view.py, let’s say you only allow registered users to subscribe then the view will go something like this (assuming you are not expecting any other request from the home URL).
def home(request):
user=request.user
if request.method == "POST":
if user.is_authenticated:
email = request.POST['sub_email'] #Using name of input
#Logic to save this email
return HttpResponse("You are Subscribed",status=200)
else:
return HttpReposnse("You are not Authenticated",status=401)
else:
return render(request,"home.html")
Now as you are the expert of simple forms, let’s work with Django class-based forms.
These views are a little work when you have very few inputs, but they are a great help in manageability and when you have to work with large number of inputs.
You will request these Class Based Forms as in your question you are trying to send an instance of a model from your Models.py to a form to user.
I have a model of Posts that can be used for this example:
class Post(models.Model):
postTitle = models.CharField(max_length = 90,null=True)
subTitle = models.CharField(max_length = 160,null=True)
location = models.CharField(max_length = 3,default = 'IN',null=True)
Now according to your question, you are trying to let the user change one attribute, let’s say postTitle and for location you are not letting the user select one of the countries which is preselected and for your post.
Now we have to create a form for this. Forms in class based are created in Forms.py. If you don't have forms.py then you can create one right along models.py and views.py.
Now for the form, I would like to edit some existing data as you are saying one of the attributes (Fields) is fixed and another editable, but you get the value from the model.
class PostEditForm(ModelForm):
location = forms.CharField(label='Country ',widget=forms.Select(attrs={'class': 'Classes_HERE','placeholder':' Select a Country','disabled':'disabled'} ,choices=country_list),required=True)
class Meta:
model = Post
fields= ['postTitle','subTitle','location']
labels = {
'postTitle':'Title',
'subTitle':'Sub-Title',
}
widgets = {
'postTitle': forms.TextInput(attrs={'class': 'mention_class_here','placeholder':' Add Title'}),
'subTitle': forms.TextInput(attrs={'class': 'mention_class_here','placeholder':' Add Sub-Title'})
}
Attributes can be mentioned in forms fields the way I have mentioned them in the above example. I used disabled="disabled" to disable (not editable) location field and used forms.Select to make it drop down.
You might also see that I gave the location field a list to choose from. This is how you can create a list of your items. It's been quite some time when I wrote this, so there might be errors or it may not work for you, so just make sure you are referring to the current documentation and searching Stack Overflow for answers.
country_list = [
('', 'Select a Country'),
("AF", "Afghanistan"),
("AX", "Aland Islands"),
("AL", "Albania"),
("DZ", "Algeria"),
("AS", "American Samoa"),
("AD", "Andorra"),
("AO", "Angola"),
("AI", "Anguilla"),
("AQ", "Antarctica"),
("AG", "Antigua And Barbuda"),
("AR", "Argentina"),
("AM", "Armenia"),
("AW", "Aruba"),
.
.
.
Now this form can be passed as context in a view to an HTML page.
def editPost(request,post_id):
user=request.user
post = get_object_or_404(Post,id=post_id) #Getting the instance of Post
if user.is_authenticated:
formPost = PostEditForm(request.POST or None,instance=post)
if request.method=='POST':
if formPost.is_valid():
savedPost=formPost.save()
else:
return render(request,'postEdit.html',{'formPost':formPost})
else:
return HttpResponse("Not Authorized",status:401)
Now your HTML file postEdit.html should look something like this:
<form id="post-form" method="POST" enctype="multipart/form-data">
{% csrf_token %}
<div>
{{formPost}}
</div>
</form>
That is it and adding a submit button in the same form, you can now edit your instance of post that you passed along with this {{formPost}}. Combine your logic wherever you think needs a change to fit in what you want to do.
By no means I am saying all this code is in working condition, but it is shown only to illustrate the flow and working.

Django - add context to request to be used by the view

Using Django I want to implement some middleware that will calculate some context that is to be used by the view itself.
For example, I have a middleware that looks at the request, and adds the user's permissions to the request, or some user configuration. The view looks at these permissions and decides how to handle the request using it.
This saves the need for multiple views (and multiple parts within the view) to query for this information.
I'm wondering what is the correct way to do that. One option is to just add request.user_permissions=... directly on the request. But is there some documented and expected way to do that?

There's no real documented way to do that, but Middleware is the correct place to do it and just adding properties to the request object is also the correct way.
You can confirm this, because Django is already doing it:
LocaleMiddelware
AuthenticationMiddleware
RemoteUserMiddleware
CurrentSiteMiddleware
SessionMiddleware
So just pick whatever is the most convenient data structure for your use case and tack that on to the request object.

This is not a perfect answer but at my experience I use this code. Every permission is saved in a boolean value which is true or false. You can access it in a html template like.
{% if request.user.is_admin %}
"Your code here"
{% else %}
"Your code here"
{% endif %}
and to send extra context you should create and pass an dicionary and pass it as as an argument to the render method from the view.
For eg:
def view(request, slug):
context = {'administrator':True}
blog_post = get_object_or_404(BlogPost, slug=slug)
context['blog_post'] = blog_post
return render(request, 'blog/detail_blog.html', context)
and access it like
{% if context.administrator %}
"Your code here"
{% else %}
"Your code here"
{% endif %}

I believe, since your middleware will calculate context, it should be implemented as context processor.
https://docs.djangoproject.com/en/3.1/ref/templates/api/#using-requestcontext
https://docs.djangoproject.com/en/3.1/ref/templates/api/#writing-your-own-context-processors

Django CreateView with get_success_url not working for this specific case

I'm using Django 2.1.
I'm having a problem with a CreateView because I need to redirect to the update url, but that url contains one argument that is created manually after verifying that the form is valid.
This is the view code:
class ProjectCreateInvestmentCampaignView(LoginRequiredMixin, SuccessMessageMixin, generic.CreateView):
template_name = 'webplatform/project_edit_investment_campaign.html'
model = InvestmentCampaign
form_class = CreateInvestmentCampaignForm
success_message = 'Investment campaign created!'
def get_success_url(self):
return reverse_lazy('project-update-investment-campaign',
args=(self.kwargs['pk'], self.object.campaign.pk, self.object.pk))
def form_valid(self, form):
project = Project.objects.get(pk=self.kwargs['pk'])
form.instance.investment_type = "A"
form.instance.contract_type = "CI"
form.instance.history_change_reason = 'Investment campaign created'
valid = super(ProjectCreateInvestmentCampaignView, self).form_valid(form)
if valid:
campaign = CampaignBase.objects.create(project=project, )
form.instance.campaign = campaign
form.instance.campaign.project = project
form.instance.campaign.creation_date = timezone.now()
form.save()
return valid
As you can see, on the form_valid I validate first the form, and then I create the object campaign and assign all the related data. This is working fine.
The problem came when I changed the get_success_url to fit my use case, that is redirecting to the update view.
I debugged and saw that at the moment I create the variable valid on the form_valid, it checks the success url, and that triggers me the following error:
Exception Type: AttributeError
Exception Value:
'NoneType' object has no attribute 'pk'
Exception Location: /Volumes/Archivos/work/i4b/webplatform/views/investor_campaign_views.py in get_success_url, line 25
I asume that the error is because the campaign is not created yet so it's trying to get the pk from a non existing object.
The thing is that I cannot create the campaign if the form is not validated, but I need the campaign to make the url working (that url is working as it is on the UpdateView that I already have).

It will only invoke get_success_url after form_valid. So it's up to form_valid to create and save the objects needed. If it's valid for them not to be created, you need a different approach. Maybe initialize (say) self.campaign_pk = 0, update it if a campaign can be created with the pk of the campaign object, and let the next view sort out what to do when pk==0. Or,
...
args=(self.kwargs['pk'],
self.object.campaign.pk if self.object.campaign else 0,
self.object.pk))
(I don't fully follow your code so I might be barking up the wrong tree here)
It may be that you don't want CreateView but FormView, which doesn't handle object creation for you, so you may find greater flexibility over how to process a valid form that nevertheless cannot be fully honoured all the time. Or even, just a plain old function-based view, in which you can process two or more forms and be far more able to decide on conditions that constitute non-validity even after all the forms have technically validated.
This is a function-based view structure I have used where I have two forms to process, and a fairly long but boring set of operations to do after BOTH forms validate:
def receive_view( request):
# let's put form instantiation in one place not two, and reverse the usual test. This
# makes for a much nicer layout with actions not sandwiched by "boilerplate"
# note any([ ]) forces invocation of both .is_valid() methods
# so errors in second form get shown even in presence of errors in first
args = [request.POST, ] if request.method == "POST" else []
batchform = CreateUncWaferBatchForm( *args, layout=CreateUncWaferBatchLayout )
po_form = CreateUncWaferPOForm( *args, layout = CreateUncWaferPOLayout, prefix='po')
if request.method != "POST" or any(
[ not batchform.is_valid(), not po_form.is_valid() ]):
return render(request, 'wafers/receive_uncoated.html', # can get this out of the way at the top
{'batchform': batchform,
'po_form': po_form,
})
#it's a POST, everything is valid, do the work
...
return redirect('appname:viewname', ...)

For me, get_success_url was not invoked as the form was not valid (was invalid) and I didn't know. You can override form_invalid(self, form) to control the behavior.
Also, consider this block of code to show any errors in your template
{% if form.errors %}
<div class="alert alert-danger" role="alert">
{% for field, errors in form.errors.items %}
{% for error in errors %}
<b>{{ field }}</b>: {{ error }}
{% endfor %}
{% endfor %}
</div>
{% endif %}

I want to use the if statement based on the existence of a web page

So basically i have a complicated scenario. I am current using Django to build a website and i have current made two apps. Both apps have almost identical fields. The field I would want to focus on though is the Information field(which they both have and which i have auto generated with the help of the Wikipedia model)
So the case here is that I want to create an if and else statement in the html in such a way that if the page i am hyperlinking to exists it would go to the link dealing with DetailView but if it doesnt exist I would redirected to the Create View
I should also note that the two apps have their names linked with the help of the foreign key but when i try to open information links using the same name , they gave me different pks
I dont feel like i explained my problem well enough but I hope someone can understand what i mean
UPDATE
ok I create the get function using
def get(self, request, *args, **kwargs):
try:
self.object = self.get_object()
except Http404:
return redirect('/create/')
context = self.get_context_data(object=self.object)
return self.render_to_response(context)
but i dont know how to use the CreateView fuction i created instead of the link i put
This is the Detail View Html
{%extends "home.html"%}
{%block head_title%} {{block.super}}{%endblock head_title%}
{% block content%}
<!-- verify authentication -->
{% if request.user.is_authenticated%}
<h3>{{object.title}}</h3><br/>
{% endif %}
<ul type="disc">
<div class="container">
<li><b>Artist: </b>{{object.Summary}}</li>
<li><b>Genre: </b>{{object.Genre}}</li>
<li><b>Bio: </b><br>{{object.Bio}}</li>
EDIT
</div>
</ul>
{%endif%}
{% endblock %}
This is my model
from django.db import models
from django.conf import settings
from Blog.models import MainPage
from django.urls.base import reverse
from Blog.Retrieve import retriever
from django.db.models.signals import pre_save,post_save
import InfoPedia
class InfoPedia(models.Model):
user =models.ForeignKey(settings.AUTH_USER_MODEL,on_delete=models.CASCADE)
Name =models.ForeignKey(MainPage,on_delete=models.CASCADE)
Location =models.CharField(max_length= 50,null=True,blank=True)
Information =models.TextField(null=True,blank=True)
TrackListing=models.TextField(null=True,blank=True)
Published=models.BooleanField(default=True)
Timestamp=models.DateTimeField(auto_now=True)
Updated=models.DateTimeField(auto_now=True)
def get_absolute_url(self):
# return f"/Blog/{self.slug}"
return reverse('InfoPedia:DetailView', kwargs={"pk":self.pk})
class Meta:
ordering=["-Updated","-Timestamp"] #orranges in order of updated
def get_tracklist(self):
return self.TrackListing.split(",")
def Information_create_pre_save( instance, sender, **kwargs):
instance.Information=retriever(instance.Name)
def rl_post_save_reciever(sender, instance,created,*args,**kwargs):
print("saved")
print(instance.Timestamp)
pre_save.connect(Information_create_pre_save, sender=InfoPedia)
post_save.connect(rl_post_save_reciever, sender=InfoPedia)

An alternative - rather than checking the if/else in the HTML, just make all the links to the DetailView URL.
Then, in the get() handler for the DetailView, you perform a queryset lookup for the object. If no object is found, then instead of displaying the DetailView HTML, return to the user a 302 redirect (i.e. a temporary redirect) to the CreateView for that object. So all your if/else logic is in the view function or class, instead of HTML.

Display html form with bound data using django

I have django form, but in my HTML i added one extra input field (directly added in html page) which i can access it using request.POST.get('extra_field_name') in my django views.
If form.is_valid() is false i can get the form as HTML with the data displayed in the HTML but with empty value for the extra added field( directly added in html page)
How can i get the bounded form data for this newly added extra html field after validation fials.
Please provide your suggestions?

View:
html_added_field = ''
error_added_field = None
if request.method == 'POST':
html_added_field = request.POST.get('extra_field_name')\
if form.is_valid():
pass
else:
error_added_field = _('Error')
context = {'html_added_field':html_added_field,'error_added_field':error_added_field}
HTML:
<input type="text" value="{{ html_added_field }}" />{% if error_added_field %}<div class="error">{{ error_added_field }}</div>{% endif %}

This article by Bennett may help you.
http://www.b-list.org/weblog/2008/nov/09/dynamic-forms/
Briefly, you have to override the __init__ method of your form, adding there the new "extra_field_name". The fields are included in the self.fields list, so doing:
self.fields['extra_field_name'] = forms.CharField(put_here_definitions_for_your_field)
should do the trick.

Honestly the best way would be for your base django form to handle the extra field. Not using extra fields in the html. However if you can't/don't want, as xbello states, in http://www.b-list.org/weblog/2008/nov/09/dynamic-forms/ you have various tricks for handling dynamic fields.
I found more robust to use the form factory method. A function that generates a dynamic form, prepared for more future changes. Still, you have to decide the best approach :-)