Django model form many to many field data how to insert?

Branch Model which to separate to data branch wise

class Branch(models.Model): # Branch Master
status_type = (
("a",'Active'),
("d",'Deactive'),
)
code = models.CharField(max_length=100, null=True, blank=True, default=None)
name = models.CharField(max_length=100, unique=True)
suffix = models.CharField(max_length=8, unique=True)
Remark = models.CharField(max_length=200, null=True, blank=True)
created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
create_at = models.DateTimeField(auto_now_add=True)
update_at = models.DateTimeField(auto_now=True)
status = models.CharField(max_length=1, choices = status_type, default = 'a')
def __str__(self):
return self.name

Vendor Model which is I am use to separate branch wise vendors

class Vendor(models.Model):
status_type = (
("a",'Active'),
("d",'Deactive'),
)
code = models.CharField(max_length=100, null=True, blank=True, default=None)
branch = models.ManyToManyField(Branch)
company = models.CharField(max_length=200)
name = models.CharField(max_length=200)
phone = models.CharField(max_length=11, unique = True)
email  =  models.EmailField(max_length=254, unique = True)
gst = models.CharField(max_length=15, unique = True)
pan_no = models.CharField(max_length=10, unique = True)
add_1 = models.CharField(max_length=50, null=True, blank = True)
add_2 = models.CharField(max_length=50, null=True, blank = True)
add_3 = models.CharField(max_length=50, null=True, blank = True)
city = models.CharField(max_length=50, default=None)
state = models.CharField(max_length=50, default=None)
Remark = models.CharField(max_length=200, null=True, blank=True)
created_by = models.ForeignKey(User, on_delete=models.CASCADE)
create_at = models.DateTimeField(auto_now_add=True)
update_at = models.DateTimeField(auto_now=True)
status = models.CharField(max_length=1, choices = status_type, default = 'a')

**this is forms.py file **

    class VendorForm(ModelForm):
class Meta:
model  = Vendor
fields = '__all__'
labels = {
'add_1':'Address',
'add_2':'Address',
'add_3':'Address',
}
exclude = ['created_by']
widgets = {
'branch':forms.CheckboxSelectMultiple(attrs={'class':'',}),
'company':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Company Name'}),
'name':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Name'}),
'phone':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Phone'}),
'email':forms.EmailInput(attrs={'class':'form-control', 'placeholder':'Email'}),
'gst':forms.TextInput(attrs={'class':'form-control', 'placeholder':'GST No.'}),
'pan_no':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Pan No.'}),
'add_1':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Address'}),
'add_2':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Address'}),
'add_3':forms.TextInput(attrs={'class':'form-control', 'placeholder':'Address'}),
'city':forms.TextInput(attrs={'class':'form-control', 'placeholder':'City'}),
'state':forms.TextInput(attrs={'class':'form-control', 'placeholder':'State'}),
'Remark':forms.Textarea(attrs={'class':'form-control','rows':'2', 'placeholder':'Remark'}),
'status':forms.Select(attrs={'class':'form-control'}),
}

**View.py Many to Many field is not insert i don't know what is problem vendor data is save but branch is field is not save **

def Add_Vendor(request): # for vendor add
if request.method == "POST":
try:
form = VendorForm(request.POST)
if form.is_valid:
forms = form.save(commit=False)
forms.created_by = request.user
forms.save()
messages.success(request,'Vendor has been added.')
return redirect('vendor_page')
except:
messages.error(request, str(form.errors))
print(form.errors)
else:
form = VendorForm()
context = {
'form':form,
'branch_data':request.session['branch_name'],
'btn_type':'fa fa-regular fa-plus',
'form_title':'Vendor Form',
'tree_main_title':'Vendor',
'v_url':'vendor_page',
'tree_title':'Add Form',
}
return render(request, 'base/vendor_master/form_vendor.html', context)

**Vendor data save into data base but branch field is not insert into database **

Just like the previous time, don't use commit=False: it prevents saving the many-to-many fields by default.

Your if form.is_valid will always succeed, since it is a method, and a method has truthiness True:

<pre><code>def Add_Vendor(request): # for vendor add
branch = get_object_or_404(Branch, pk=request.session['branch_id'])
if request.method == 'POST':
form = VendorForm(request.POST, request.FILES)
if form.is_valid():
form.instance.created_by = request.user
vendor_add = form.save()
<b>vendor_add.branch.add(branch)</b>
messages.success(request, 'Vendor has been added.')
return redirect('vendor_page')
else:
messages.error(request, str(form.errors))
print(form.errors)
else:
form = VendorForm()
context = {
'form': form,
'branch_data': request.session['branch_name'],
'btn_type': 'fa fa-regular fa-plus',
'form_title': 'Vendor Form',
'tree_main_title': 'Vendor',
'v_url': 'vendor_page',
'tree_title': 'Add Form',
}
return render(request, 'base/vendor_master/form_vendor.html', context)</code></pre>

That being said, session variables are often not a good idea. Indeed, it creates some sort of global state antipattern [softwareengineering.se], and it is not unthinkable that just before a person makes a request to the page, through some other page view, the session variables change/invalidate. Therefore giving the wrong impression that it will work with a different branch. Usually it is better to do things explicitly and thus add a parameter to the path that contains the primary key, or some other token of the branch to add.

The Branch model is however not suposed to update, it simply adds a link. That means that myvendor.branch.all() should now return that Branch, it thus links the two together, linking two items does not modify the (individual) items, hence the timestamp will not update.

> Note: Functions are normally written in snake_case, not PascalCase, therefore it is
> advisable to rename your function to add_vendor, not <s>Add_Vendor</s>.

> Note: It is normally better to make use of the settings.AUTH_USER_MODEL&nbsp;^[Django-doc] to refer to the user model, than to use the User model&nbsp;^[Django-doc] directly. For more information you can see the referencing the User model section of the documentation.

> Note: It is often better to use <code>get_object_or_404(&hellip;)</code>&nbsp;^[Django-doc],
> then to use <code>.get(&hellip;)</code>&nbsp;^[Django-doc] directly. In case the object does not exists,
> for example because the user altered the URL themselves, the <code>get_object_or_404(&hellip;)</code> will result in returning a HTTP 404 Not Found response, whereas using
> <code>.get(&hellip;)</code> will result in a HTTP 500 Server Error.

> Note: While most forms do not process media files, it is probably better to pass request.FILES&nbsp;^[Django-doc] to the form anyway, such that if you later add an extra media field, all views that use the form will indeed handle the files properly.g

there is a problem with form validation in your views.py
you should use:

if form.is_valid():

and you should make sure that the "branch_id" exists

to add branch to vendor, you should first save the vendor object without committing to database then add the branch to vendor and then save the vendor object again so the "Add_Vendor" function should be like this:

def Add_Vendor(request): # for vendor add
b_id = request.session['branch_id']
# check if b_id exists
if b_id is None:
messages.error(request, 'Branch not selected. Please select a branch first.')
return redirect('select_branch_page') # redirect to the branch selecting page
branch_id = Branch.objects.get(id = b_id)
print(branch_id)
if request.method == "POST":
form = VendorForm(request.POST)
if form.is_valid():
vendor_add = form.save(commit=False)
vendor_add.created_by = request.user
vendor_add.save()
vendor_add.branch.add(branch_id)
vendor_add.save() # Save the vendor again to persist the changes with the branch.
messages.success(request, 'Vendor has been added.')
return redirect('vendor_page')
else:
messages.error(request, str(form.errors))
print(form.errors)
else:
form = VendorForm()
context = {
'form':form,
'branch_data':request.session['branch_name'],
'btn_type':'fa fa-regular fa-plus',
'form_title':'Vendor Form',
'tree_main_title':'Vendor',
'v_url':'vendor_page',
'tree_title':'Add Form',
}
return render(request, 'base/vendor_master/form_vendor.html', context)

I hope this helps you.