Loading and saving data from m2m relationships in Textarea widgets with ModelForm

Question

I have a Model that looks something like this:

class Business(models.Model):
    name = models.CharField('business name', max_length=100)
    # ... some other fields
    emails = models.ManyToManyField(Email, null=True)
    phone_numbers = models.ManyToManyField(PhoneNumber, null=True)
    urls = models.ManyToManyField(URL, null=True)

and a corresponding ModelForm:

class BusinessContactForm(forms.ModelForm):
    emails = forms.CharField(widget=forms.Textarea(attrs={'rows':4,'cols':32}))
    phone_numbers = forms.CharField(widget=forms.Textarea(attrs={'rows':4,'cols':32}))
    urls = forms.CharField(widget=forms.Textarea(attrs={'rows':4,'cols':32}))

    class Meta:
        model = Business
        fields = ['emails', 'phone_numbers', 'urls',]

My question: What is the best way to load the existing emails, phone_numbers, and urls into the Textarea widgets when presenting the form (one per line in their respective widgets)?

Then, after the form has been modified and submitted, what is the best way to make sure to add any new emails, numbers, or urls (m2m relationships) and remove any that are no longer in the list (also making sure not to add duplicates)?

Answer 1

This is not directly an answer to your question. It is more a suggestion to re-think your data model.

It looks like your BusinessContactForm presents textarea widgets to insert multiple rows into the database. I would not use a Textarea widget for multiple items of more restricted type: I'd enter phone numbers with a phone number widget, URLs with a URL widget, and emails with an email widget.

A business contact is really a person who works for a company and has an email address and phone number, correct? So why not model the business contact like that and have a foreign key to the business?

That's more of the approach I would take.

Answer 2

This really isn't a good way to do it. Dealing with related items on forms is what formsets are for.

Instead of defining the related fields as extra fields on the BusinessForm model, use a standard form for a contact, with email, phone and url. Then pass this into the modelformset_factory to create an inline formset for your BusinessContact form.