If you dynamically add a field to a WTForms form, the newly-added fields are not validated (even if you add validators).
For instance, in Flask:
#app.route('/add', methods=['GET', 'POST'])
def add():
if 'state' not in session:
session['state'] = 1
form = MyForm()
if request.method == 'POST' and form.validate():
if session['state'] == 1:
setattr(
MyForm,
'asd',
StringField(
'asdfield',
validators = [
DataRequired(),
Length(min=1)
]
)
)
form = MyForm()
session['state'] = 2
return render_template(
'add.html',
form=form
)
print(len(form.asd.data)) # can equal 0
session['state'] = 1
return redirect('/add')
return render_template(
'add.html',
form=form
)
I believe this is due to the fact that form = MyForm() is run every time you go to /add, so even if session['state'] == 2 you run form.validate() on a default form which does not have the dynamically-added field. Therefore, this field cannot be part of the form validation process.
How can one properly address this behaviour ? If it's not possible, then how can one dynamically add fields to an existing form in such a way that all fields get properly validated upon submission ?
Since you call validate() before adding the field, naturally, you can't validate a field which doesn't exist yet. That said, you don't want to add a field to an instance instead of a class. This is because since WTForms processes its input data at construction, adding fields to the instance is mostly a meaningless thing.
If your field name is static, you can use the del trick detailed here
If it's dynamic, you could instead follow the dynamic form composition pattern from the docs.
Since I've gone over this in detail, I'll link my previous example here:
Wtfforms dynamic generation
Related
I am using formset to input my data into the database but for some reason it just doesn't validate, whenever I test in the terminal and call the .is_valid() It just returns false no matter what I try. Here's the code in my views.py and forms.py . Any help will be much appreciated!
# Advanced Subjects (Advanced Biology)
def form_5_entry_biology_view(self, request):
current_teacher = User.objects.get(email=request.user.email)
logged_school = current_teacher.school_number
students_involved = User.objects.get(school_number=logged_school).teacher.all()
data = {"student_name": students_involved}
formset_data = AdvancedStudents.objects.filter(class_studying="Form V", combination="PCB")
student_formset = formset_factory(AdvancedBiologyForm, extra=0)
initial = []
for element in formset_data:
initial.append({"student_name": element})
formset = student_formset(request.POST or None, initial=initial)
print(formset.is_valid())
context = {
"students": students_involved,
"formset": formset,
"class_of_students": "Form V",
"subject_name": "Advanced Biology",
}
return render(request, "analyzer/marks_entry/marks_entry_page.html", context)
And here is my forms.py
class AdvancedBiologyForm(forms.ModelForm):
student_name = forms.CharField()
class Meta:
model = ResultsALevel
fields = ('student_name', 'advanced_biology_1', 'advanced_biology_2',
'advanced_biology_3',)
Before using request.POST and is_valid() you probably want to check if there actually is a post request or if the page is just viewed:
def form_5_entry_biology_view(self, request):
current_teacher = User.objects.get(email=request.user.email)
logged_school = current_teacher.school_number
students_involved = User.objects.get(school_number=logged_school).teacher.all()
data = {"student_name": students_involved}
formset_data = AdvancedStudents.objects.filter(class_studying="Form V", combination="PCB")
# Here you are creating the formset using the model
student_formset = formset_factory(AdvancedBiologyForm, extra=0)
# Here you are generating your initial data
initial = []
for element in formset_data:
initial.append({"student_name": element})
# Here you are using the initial data to create pre-populated
# forms with it using the formset.
# These forms will be displayed when the page loads.
formset = student_formset(initial=initial)
context = {
"students": students_involved,
"formset": formset,
"class_of_students": "Form V",
"subject_name": "Advanced Biology",
}
# But if the user hits the "submit"-Button...
if request.method == 'POST':
# ... you don't want to have the formset with your
# initial data. Instead you want the entries by the user
# which are transmitted in request.POST to populate the
# formset forms.
formset = student_formset(request.POST or None)
# Now you can validate the formset with the fields which
# got input the the user; not the "initial" data like in
# your original code
if formset.is_valid():
# This runs formset validation.
# You can define your own formset validations like
# you would for models/forms.
for form in formset:
# And / Alternatively:
# you could in theory also add another "if form.is_valid():" in here
# This would trigger any validation on the
# model/form; not the validators on the formset.
form.save()
return HttpResponseRedirect(...
return render(request, "analyzer/marks_entry/marks_entry_page.html", context)
Otherwise you might call is_valid() on an unbound form.
From Django docs:
If the form is submitted using a POST request, the view will once again create a form instance and populate it with data from the request: form = NameForm(request.POST) This is called “binding data to the form” (it is now a bound form).
Basically if a form is empty it's unbound, and if it's populated with data it gets bound after POST. When you open a page and immediately try "is_valid()" it will basically always be false as you are checking if an empty form is valid; which it likely never is.
To point out the error:
formset = student_formset(request.POST or None, initial=initial)
print(formset.is_valid())
This is not valid. Because initial values are not equal to populating a form field with "real" values. So what happens is that it tries to populate the fields in the form with request.POST or None.
But you don't have a if request.method == 'POST': condition. So your code will just run through before hitting the last line of code which is the return statement displaying the page.
This means that your code validates request.POST or None before the user even saw the page. So there is no way a user could have already entered data and hit submit. Which means there is no POST-request, so it always turns None. So you are basically calling is_valid() on a form that has no field values in it which leads to the validation failing.
EDIT 1: I just noticed in your forms.py you have written:
fields = ('student_name', 'advanced_biology_1', 'advanced_biology_2',
'advanced_biology_3',)
This should be a list instead:
fields = ['student_name', 'advanced_biology_1', 'advanced_biology_2',
'advanced_biology_3',]
EDIT 2: fixed wrong variable name
EDIT 3: added extensive comments to clarify what's happening in the code
EDIT 4: pointed out cause of problem more distinctly.
Let's say I have a Django form with ChoiceField:
class MyForm(forms.Form):
name = forms.CharField(label="Name", required=True)
some_object = forms.ChoiceField(label="Object", choices=[(0, '-----')] + [(x.id, x.name) for x in Obj.objects.all()])
Choisefield is being initialized with list of objects headed by 'empty choice'. There is no object with pk=0.
In that form I have a clean() method:
def clean(self):
if not Obj.objects.filter(self.cleaned.data['some_object'].exists():
self.errors.update({'some_object': ['Invalid choice']})
It works well when I'm sending a form to a server, if data in it doesn't match conditions, field.is_valid returns False and I render form with error messages. But, when I create an empty form like this:
if request.method == 'GET':
data = {'name': 'Untitled',
'some_object': 0}
form = MyForm(data)
return render(request, 'app\template.html', {'form': form})
Django renders form with error message ('Invalid choice') even though form was just created and 'Object' select was intended to be set in empty position. Is it possible to disable form clean() method in specific cases? Or maybe I'm doing this all wrong? What is the best practice to create an empty form?
The problem is that a form with any data dictionary passed to it counts as a "bound" form, against which Django will perform data validation. See here for details: https://docs.djangoproject.com/en/2.1/ref/forms/api/#bound-and-unbound-forms
You want an "unbound" form - to have default initial values in here, just set the initial property on your form fields. See full details here: https://docs.djangoproject.com/en/2.1/ref/forms/fields/#initial
I'm trying to run a simple update form that should update all object values in DB submitted from the form.
This is my update view that does nothing other than redirecting to the "/". No errors but no update either.
def update(request, business_id):
if request.method == 'POST':
form = BusinessForm(request.POST)
if form.is_valid():
t = Business.objects.get(id=business_id)
t.save()
return HttpResponseRedirect("/")
else:
...
You are not updating any fields, use form.cleaned_data to get the form field values:
Once is_valid() returns True, the successfully validated form data
will be in the form.cleaned_data dictionary. This data will have been
converted nicely into Python types for you.
if form.is_valid():
t = Business.objects.get(id=business_id)
t.my_field = form.cleaned_data['my_field']
t.save()
Also, consider using an UpdateView class-based generic view instead of a function-based:
A view that displays a form for editing an existing object,
redisplaying the form with validation errors (if there are any) and
saving changes to the object. This uses a form automatically generated
from the object’s model class (unless a form class is manually
specified).
The Django doc mention that a Model AutoField will not be represented in a form built with a ModelForm.
When editing and saving that form, how should I supposed to know the underlying AutoField id value to save correctly my form data to database?
I know I can inject myself in the edit form an hidden field to know which row has been edited but is there a way Django manage that hidden field or some other mecanism automatically?
Thanks a lot
Etienne
You do that by specifying the instance=<> parameter when you are using ModelForm.
More on this in the documentation here
Example usage of a create/update view:
def myview(request, id=None):
if id:
obj_to_edit = MyModel.objects.get(id=1)
form = MyForm(instance=obj_to_edit)
else:
obj_to_edit = None
form = MyForm()
if request.method == 'POST':
if id: #update
form = MyForm(request.POST, instance=obj_to_edit)
else: #create
form = MyForm(request.POST)
#rest of the code
and the URL would have something like:
url(r'/blah/create/', 'myview'),
url(r'/blah/edit/(?P<id>[\d+])/', 'myview')
Now, django understands that it needs to edit rather than create new objects.
Also note that if you are using forms.Form, you would have to manually query for the unique fields, or inject the hidden id field as you have mentioned.
Usually when you're editing a form the specific instance that you want to edit will be identified in your URL using either the primary key or a slug field, e.g:
www.example.com/model/edit/6/
or
www.example.com/model/edit/object_slug/
You would then set up your urls.py to pass that parameter to your view, where you would use the example provided by karthkir (I'll use the primary as the example from here)
urls.py
urlpatterns = patterns('',
url(regex=r'^model/edit/(?P<pk>\d+)/$', 'myapp.views.myview', name='add_customer'),
)
views.py
def myview(request, pk):
obj_to_edit = MyModel.objects.get(id=pk)
...
I've made a nice form, and a big complicated 'add' function for handling it. It starts like this...
def add(req):
if req.method == 'POST':
form = ArticleForm(req.POST)
if form.is_valid():
article = form.save(commit=False)
article.author = req.user
# more processing ...
Now I don't really want to duplicate all that functionality in the edit() method, so I figured edit could use the exact same template, and maybe just add an id field to the form so the add function knew what it was editing. But there's a couple problems with this
Where would I set article.id in the add func? It would have to be after form.save because that's where the article gets created, but it would never even reach that, because the form is invalid due to unique constraints (unless the user edited everything). I can just remove the is_valid check, but then form.save fails instead.
If the form actually is invalid, the field I dynamically added in the edit function isn't preserved.
So how do I deal with this?
If you are extending your form from a ModelForm, use the instance keyword argument. Here we pass either an existing instance or a new one, depending on whether we're editing or adding an existing article. In both cases the author field is set on the instance, so commit=False is not required. Note also that I'm assuming only the author may edit their own articles, hence the HttpResponseForbidden response.
from django.http import HttpResponseForbidden
from django.shortcuts import get_object_or_404, redirect, render, reverse
#login_required
def edit(request, id=None, template_name='article_edit_template.html'):
if id:
article = get_object_or_404(Article, pk=id)
if article.author != request.user:
return HttpResponseForbidden()
else:
article = Article(author=request.user)
form = ArticleForm(request.POST or None, instance=article)
if request.POST and form.is_valid():
form.save()
# Save was successful, so redirect to another page
redirect_url = reverse(article_save_success)
return redirect(redirect_url)
return render(request, template_name, {
'form': form
})
And in your urls.py:
(r'^article/new/$', views.edit, {}, 'article_new'),
(r'^article/edit/(?P<id>\d+)/$', views.edit, {}, 'article_edit'),
The same edit view is used for both adds and edits, but only the edit url pattern passes an id to the view. To make this work well with your form you'll need to omit the author field from the form:
class ArticleForm(forms.ModelForm):
class Meta:
model = Article
exclude = ('author',)
You can have hidden ID field in form and for edit form it will be passed with the form for add form you can set it in req.POST e.g.
formData = req.POST.copy()
formData['id'] = getNewID()
and pass that formData to form