I have a form called Vehicles and i'm trying to assign a unique id to each one, each time a user completes one.
class Vehicles(models.Model):
id = models.DecimalField(primary_key=True, unique=True)
Trying to avoid race conditions(when two forms are being submitted in the same time) after the initial value that I assign to the id field according to the last vehicle-db-record, before saving the form I query again the db for the id of the last record. More or less I do it this way:
def vehicle(request):
vehicles= Vehicles.objects.all().order_by("-id")[0]
id = vehicles.id+1
if request.method == 'POST':
form = VehiclesForm(data=request.POST)
if form.is_valid():
vehicles= Vehicles.objects.all().order_by("-id")[0]
id = vehicles.id+1
temp = form.save(new_veh_id=id)
return render_to_response('success.html', locals(), context_instance= RequestContext(request))
else:
form = VehiclesForm(initial={'id': id})
return render_to_response('insertVehicle.html', locals(), context_instance= RequestContext(request))
and in forms I override the save method:
def save(self, *args, **kwargs):
commit = kwargs.pop('commit', True)
new_veh_id = kwargs.pop('new_veh_id', None)
instance = super(VehiclesForm, self).save(*args, commit = False, **kwargs)
if id is not None: instance.id = new_veh_id
if commit:
instance.save()
return instance
but is_valid returns false with form error:vehicles with this id already exists.
I use exactly this practice with another model and form (identical fields to these) and it works like a charm, forms pass validation despite the same id and it changes it in the last submitted form. Can anyone help me on this or suggest a better solution to achieve this functionality? What I do is maybe somehow 'custom'.
EDIT: I also tried this, but is_valid fails again
def clean(self):
cleaned_data = super(VehiclesForm, self).clean()
id = unicode(self.cleaned_data.get('id'))
vehicles= Vehicles.objects.all().order_by("-id")[0]
id = vehicles.id+1
cleaned_data[id] = id
return cleaned_data
I think you need select_for_update which locks the rows until the end
of transaction. Mind you that although it is designated to work with many
rows, you can still lock just one row, by making sure your filter query
will return only one object.
Related
I have a survey app - you create a Survey and it saves the Response. It's registered in Django Admin. I can see the Survey and submit a Response. When I click Response in Admin, I get the following error:
ValueError at /admin/django_survey/response/
Cannot query "response 5f895af5999c49929a522316a5108aa0": Must be "User" instance.
So I checked the SQL database and for django_survey_response I can see that there is a response, but the column user_id is NULL.
I suspected that there's an issue with my Views and/or Forms and I'm not saving the logged in User's details, so I've tried to address that.
However, now I get
NameError at /survey/1/
global name 'user' is not defined
How do I resolve this? I want the form to save Response with the logged in user's ID.
The Traceback:
django_survey\views.py
def SurveyDetail(request, id):
survey = Survey.objects.get(id=id)
category_items = Category.objects.filter(survey=survey)
categories = [c.name for c in category_items]
print 'categories for this survey:'
print categories
if request.method == 'POST':
form = ResponseForm(request.POST, survey=survey) <.........................
if form.is_valid():
response = form.save()
return HttpResponseRedirect("/confirm/%s" % response.interview_uuid)
else:
form = ResponseForm(survey=survey)
print form
django_survey\forms.py
def __init__(self, *args, **kwargs):
# expects a survey object to be passed in initially
survey = kwargs.pop('survey')
self.survey = survey
self.user = user <.........................
super(ResponseForm, self).__init__(*args, **kwargs)
self.uuid = random_uuid = uuid.uuid4().hex
# add a field for each survey question, corresponding to the question
# type as appropriate.
data = kwargs.get('data')
It might be worth noting that previously, instead of user, the model's field was called interviewee. I changed this and ran migrations again.
I am also using userena.
The error message in this instance is python trying to tell you that you are attempting to access a variable user that has not been defined in the scope of your method.
Let's look at the first few lines of the __init__() method:
def __init__(self, *args, **kwargs):
# expects a survey object to be passed in initially
survey = kwargs.pop('survey')
self.survey = survey
self.user = user
We can see where the survey variable is defined: survey = kwargs.pop('survey'). It is passed into the form as a keyword argument and extracted in the forms __init__. However underneath you attempt to do the same thing with user but haven't actually defined it above. The correct code would look like:
def __init__(self, *args, **kwargs):
# expects a survey object to be passed in initially
survey = kwargs.pop('survey')
user = kwargs.pop('user')
self.survey = survey
self.user = user
However, this still won't work because we aren't passing the user variable to the form via kwargs. To do that we pass it in when we initialise the form in your views.py. What isn't clear is what user object you are expecting to pass in. the request.user? or does the Survey object have a user attribute? in which case you would not need to pass user in and would just use survey.user etc.
django_survey\views.py
def SurveyDetail(request, id):
survey = Survey.objects.get(id=id)
category_items = Category.objects.filter(survey=survey)
categories = [c.name for c in category_items]
print 'categories for this survey:'
print categories
if request.method == 'POST':
form = ResponseForm(request.POST, survey=survey, user=request.user)
if form.is_valid():
response = form.save()
return HttpResponseRedirect("/confirm/%s" % response.interview_uuid)
else:
form = ResponseForm(survey=survey, user=request.user)
print form
In your view when you initialize your form you need to pass it the user (current user in this case)? similar to this form = ResponseForm(request.POST, survey=survey, user=request.user). Then in the __init__ of your form pop the user object user = kwargs.pop('user'). I believe that will resolve your issue.
THE CONTEXT
I am trying to implement a tagging system for my project. The various plug-in solutions (taggit, tagulous) are each unsuitable in some way.
I would like to allow users to select from existing tags or create new ones in a Select2 tagging field. Existing tags can be added or removed without problem. My difficulty is in the dynamic generation and assignment of new tags.
MY APPROACH
Select2 helpfully renders the manually-entered tags differently in the DOM from those picked from the database via autocomplete. So upon clicking submit, I have javascript collect the new tags and string them together in the value of a hidden input, then delete them from the Select2 field to avoid any validation errors (the form otherwise POSTs the tag names as the ids, which throws a db error).
In the view, I iterate over the desired new tags. For each entry I create the new tag, then add it to the parent object's related set.
THE PROBLEM
While this successfully creates each tag (verified via Admin) it doesn't add it to the related set.
No errors are generated on the (clearly not succeeding) related set add.
The newly-generated tags are correctly instantiated and can be Select2-chosen and sucessfully assigned on a subsequent UpdateView, so I'm certain the problem lies in the view-assignment of the tags to the parent.
The same code executed via the Django shell work flawlessly, so I don't believe its a simple syntax error.
Thus the locus of the problem seems to be in the POST view code adding newly-generated tags to the parent, but I cannot see where the code goes astray.
Thanks for any insights or advice!
models.py:
class Recipe_tag(models.Model):
id = models.UUIDField(primary_key=True,default=uuid.uuid4,null=False)
tag = models.CharField('Tag name',max_length=32,null=False,unique=True)
def __str__(self):
return str(self.tag)
class Recipe_base(models.Model):
id = models.UUIDField(primary_key=True,default=uuid.uuid4,null=False)
name = models.CharField('Recipe name',max_length=128,null=False)
tags = models.ManyToManyField(Recipe_tag,related_name='recipes',null=True,blank=True)
def __str__(self):
return str(self.name)
The post portion of the view:
def post(self, request, *args, **kwargs):
self.object = None
r = Recipe_base.objects.get(id=self.kwargs.get('pk'))
form = RecipeUpdateTagsForm(request.POST,instance=r)
form_valid = form.is_valid()
if form_valid:
if form.has_changed:
f = form.save(commit=False)
clean = form.cleaned_data
f.addedTags = clean['addedTags']
if f.addedTags == 'placeholder':
pass
else:
new_tags = f.addedTags.split(',')
for new_tag in new_tags:
a = Recipe_tag(tag=new_tag)
a.save()
r.tags.add(a)
f.save()
form.save_m2m()
else:
pass
return self.form_valid(form)
else:
return self.form_invalid(form)
Doing further digging, I found a post on another site in which the OP was experiencing the same issues. The trick is to remove the m2m assignment from the "create" or "update" process entirely, because the final save() that occurs in form_valid will discard any changes to the parent's related set.
In my case, the solution was to punt the iteration/assignment of the new tags to form_valid, directly after the final save() occurs there:
def form_valid(self, form, **kwargs):
self.object = form.save()
addedTags = kwargs['addedTags']
r = Recipe_base.objects.get(id=self.kwargs.get('pk'))
if addedTags == 'placeholder':
pass
else:
new_tags = addedTags.split(',')
for new_tag in new_tags:
a = Recipe_tag(tag=new_tag)
a.save()
# print("debug // new tag: %s, %s" % (a.tag, a.id))
r.tags.add(a)
# print("debug // added %s to %s" % (a.tag,r.id))
return HttpResponseRedirect(self.get_success_url())
def get(self, request, *args, **kwargs):
self.object = Recipe_base.objects.get(id=self.kwargs.get('pk'))
recipe_name = self.object.name
recipe_id = self.kwargs.get('pk')
form = RecipeUpdateForm(instance=Recipe_base.objects.get(id=self.kwargs.get('pk')))
return self.render_to_response(self.get_context_data(form=form,recipe_name=recipe_name,recipe_id=recipe_id))
def post(self, request, *args, **kwargs):
self.object = None
r = Recipe_base.objects.get(id=self.kwargs.get('pk'))
form = RecipeUpdateForm(request.POST,instance=r)
form_valid = form.is_valid()
#print("debug // form_valid PASSED")
if form_valid:
if form.has_changed:
#print("debug // Form changed...")
f = form.save(commit=False)
#print("debug // Passes save C=F")
clean = form.cleaned_data
#print('debug // pre-existing tags: ',clean['tags'])
f.addedTags = clean['addedTags']
addedTags = clean['addedTags']
#print('debug // manual tags: ',clean['addedTags'])
f.save()
form.save_m2m()
#print("debug // Form saved")
else:
#print("debug // Form unchanged, skipping...")
pass
#print("debug // Reached successful return")
return self.form_valid(form, addedTags=addedTags,pk=r.id)
else:
#print("debug // Form fails validation")
#print("debug // Reached unsuccessful return")
return self.form_invalid(form)
I got a form as following:
class CourseAddForm(forms.ModelForm):
"""Add a new course"""
name = forms.CharField(label=_("Course Name"), max_length=100)
description = forms.Textarea()
course_no = forms.CharField(label=_("course Number"), max_length=15)
#Attach a form helper to this class
helper = FormHelper()
helper.form_id = "addcourse"
helper.form_class = "course"
#Add in a submit and reset button
submit = Submit("Add", "Add New Record")
helper.add_input(submit)
reset = Reset("Reset", "Reset")
helper.add_input(reset)
def clean(self):
"""
Override the default clean method to check whether this course has been already inputted.
"""
cleaned_data = self.cleaned_data
name = cleaned_data.get('name')
hic = cleaned_data.get('course_no')
try:
course=Course.objects.get(name=name)
except Course.DoesNotExist:
course=None
if course:
msg = u"Course name: %s has already exist." % name
self._errors['name'] = self.error_class([msg])
del cleaned_data['name']
return cleaned_data
else:
return self.cleaned_data
class Meta:
model = Course
As you can see I overwrote the clean method to check whether this course has already existed in the database when the user is trying to add it. This works fine for me.
However, when I want to add the same check for the form for editing, the problem happened. Because it is editing, so the record with same course name has already exist in the DB. Thus, the same check would throw error the course name has already exist. But I need to check the duplication in order to avoid the user updating the course name to another already existed course name.
I am thinking of checking the value of the course name to see if it is changed. If it has been changed, than I can do the same check as above. If it has not been changed, I don't need to do the check. But I don't know how can I obtain the origin data for editing.
Does anyone know how to do this in Django?
My view looks as following:
#login_required
#csrf_protect
#never_cache
#custom_permission_required('records.change_course', 'course')
def edit_course(request,course_id):
# See if the family exists:
try:
course = Course.objects.get(id=course_id)
except Course.DoesNotExist:
course = None
if course:
if request.method == 'GET':
form = CourseEditForm(instance=course)
return render_to_response('records/add.html',
{'form': form},
context_instance=RequestContext(request)
)
elif request.method == 'POST':
form = CourseEditForm(request.POST, instance=course)
if form.is_valid():
form.save()
return HttpResponseRedirect('/records/')
# form is not valid:
else:
error_message = "Please correct all values marked in red."
return render_to_response('records/edit.html',
{'form': form, 'error_message': error_message},
context_instance=RequestContext(request)
)
else:
error = "Course %s does not exist. Press the 'BACK' button on your browser." % (course)
return HttpResponseRedirect(reverse('DigitalRecords.views.error', args=(error,)))
Thank you.
I think you should just set unique=True on the Course.name field and let the framework handle that validation for you.
Update:
Since unique=True is not the right answer for your case, you can check this way:
def clean(self):
"""
Override the default clean method to check whether this course has
been already inputted.
"""
cleaned_data = self.cleaned_data
name = cleaned_data.get('name')
matching_courses = Course.objects.filter(name=name)
if self.instance:
matching_courses = matching_courses.exclude(pk=self.instance.pk)
if matching_courses.exists():
msg = u"Course name: %s has already exist." % name
raise ValidationError(msg)
else:
return self.cleaned_data
class Meta:
model = Course
As a side note, I've also changed your custom error handling to use a more standard ValidationError.
I believe excluding the current instance id from the results would solve the problem:
from django.db.models import Q
try:
qs = Course.objects.filter(name=self.cleaned_data.get('name'))
if self.instance.pk is not None:
qs = qs.filter(~Q(pk=self.instance.pk))
course = qs.get()
except Course.DoesNotExist:
course = None
However as dokkaebi pointed out, unique is really the better way to go with this, as this solution is vulnerable to race conditions. I'm not sure what your datamodel looks like but I suspect defining
class Meta:
unique_together = ('department', 'name')
should accomplish what you want.
I am using django and as I am pretty new I have some questions.
I have one model called Signatures and a ModelForm called SignatureForm in my models.py file:
class Signature(models.Model):
sig = models.ForeignKey(Device)
STATE = models.CharField(max_length=3, choices=STATE_CHOICES)
interval = models.DecimalField(max_digits=3, decimal_places=2)
verticies = models.CharField(max_length=150)
class SignatureForm(ModelForm):
class Meta:
model = Signature
widgets = {
'verticies': HiddenInput,
}
To use it, I wrote the following function in views.py:
def SigEditor(request):
# If the form has been sent:
if request.method == 'POST':
form = SignatureForm(request.POST)
# If it is valid
if form.is_valid():
# Create a new Signature object.
form.save()
return render_to_response('eQL/sig/form_sent.html')
else:
return render_to_response('eQL/sig/try_again.html')
else:
form = SignatureForm()
return render_to_response('eQL/sig/showImage.html', {'form' : form})
However, I don't want to save all the new signatures. I mean, if the user introduces a new signature of the device A and state B, I would like to check if I have some signature like that in my database, delete it and then save the new one so that I have only one signature saved for each device and state.
I have tried something like this before saving it but of course is not working:
q = Signature.objects.filter(sig = s, STATE = st)
if q.count != 0:
q.delete()
form.save()
can anyone help?? thanks!!
If you really do want to delete, why not?
Signature.objects.filter(sig=s, STATE=st).delete()
If you only ever want one combination of those items, you could use get_or_create, and pass in the instance to your ModelForm.
instance, created = Signature.objects.get_or_create(sig=s, STATE=st)
form = SignatureForm(request.POST, instance=signature)
# edit instance.
Or put it in your form save logic:
class SignatureForm(ModelForm):
def save(self, *args, **kwargs):
data = self.cleaned_data
instance, created = Signature.objects.get_or_create(sig=data['sig'], STATE=data['state'])
self.instance = instance
super(SignatureForm, self).save(*args, **kwargs)
I am using Django ModelForms to create a form. I have my form set up and it is working ok.
form = MyForm(data=request.POST)
if form.is_valid():
form.save()
What I now want though is for the form to check first to see if an identical record exists. If it does I want it to get the id of that object and if not I want it to insert it into the database and then give me the id of that object. Is this possible using something like:
form.get_or_create(data=request.POST)
I know I could do
form = MyForm(instance=object)
when creating the form but this would not work as I still want to have the case where there is no instance of an object
edit:
Say my model is
class Book(models.Model):
name = models.CharField(max_length=50)
author = models.CharField(max_length=50)
price = models.CharField(max_length=50)
I want a form which someone can fill in to store books. However if there is already a book in the db which has the same name, author and price I obviously don't want this record adding again so just want to find out its id and not add it.
I know there is a function in Django; get_or_create which does this but is there something similar for forms? or would I have to do something like
if form.is_valid():
f = form.save(commit=false)
id = get_or_create(name=f.name, author=f.author, price=f.price)
Thanks
I like this approach:
if request.method == 'POST':
form = MyForm(request.POST)
if form.is_valid():
book, created = Book.objects.get_or_create(**form.cleaned_data)
That way you get to take advantage of all the functionality of model forms (except .save()) and the get_or_create shortcut.
You just need two cases in the view before the postback has occurred, something like
if id:
form = MyForm(instance=obj)
else
form = MyForm()
then you can call form.save() in the postback and Django will take care of the rest.
What do you mean by "if an identical record exists"? If this is a simple ID check, then your view code would look something like this:
if request.method == 'POST':
form = MyForm(request.POST)
if form.is_valid():
form.save()
else:
if get_id:
obj = MyModel.objects.get(id=get_id)
form = MyForm(instance=obj)
else:
form = MyForm()
The concept here is the check occurs on the GET request, such that on the POST to save, Django will already have determined if this is a new or existing record.
If your check for an identical record is more complex, it might require shifting the logic around a bit.
I would do this -
if request.method == 'POST':
form = MyForm(request.POST)
if form.is_valid():
name = form.cleaned_data['name']
author = form.cleaned_data['author']
price = form.cleaned_data['prince']
if name and author and price:
book, created = Book.objects.get_or_create(name=name, \
author=author, price=price)
if created:
# fresh entry in db.
else:
# already there, maybe update?
book.save()
Based on the answers and comments, I had to create a different solution for my case, which included the use of unique_together on the base model. You may find this code useful as well, as I actually made it fairly generic.
I have custom code in the form.save() method that I want to utilize for creating a new object, so I don't want to simply not use the form.save() call. I do have to put my code check in the form.save() method, which I think is a reasonable place to put it.
I have a utility function to flatten iterables.
def flatten(l, a=list()):
"""
Flattens a list. Just do flatten(l).
Disregard the a since it is used in recursive calls.
"""
for i in l:
if isinstance(i, Iterable):
flatten_layout(i, a)
else:
a.append(i)
return a
In the ModelForm, I overwrite the validate_unique() method:
def validate_unique(self):
pass
This is about what my save method looks like:
def save(self, commit=True):
unique_fields = flatten(MyObject._meta.unique_together)
unique_cleaned_data = {k: v for k, v in self.cleaned_data.items() if k in unique_fields}
# check if the object exists in the database based on unique data
try:
my_object = MyObject.objects.get(**unique_cleaned_data)
except MyObject.DoesNotExist:
my_object = super(MyModelFormAjax, self).save(commit)
# -- insert extra code for saving a new object here ---
else:
for data, value in self.cleaned_data.items():
if data not in unique_fields:
# only update the field if it has data; otherwise, retain
# the old value; you may want to comment or remove this
# next line
if value:
setattr(my_object, data, value)
if commit:
my_object.save()
return my_object